THE  GIFT  OF 

FLORENCE  V.  V.  DICKEY 

TO  THE 

UNIVERSITY  OF  CALIFORNIA 
AT  LOS  ANGELES 


THE  DONALD  R.  DICKEY 

LIBRARY 
OF  VERTEBRATE  ZOOLOGY 


THE   PRINCIPLES   OF 
BIOLOGY 

VOLUME  I 


THE    PRINCIPLES   OF 
BIOLOGY 


BY 
HERBERT    SPENCER 


IN  TWO  VOLUMES 
VOLUME    I 


NEW    YORK    AND    LONDON 

D.    APPLETON     AND     COMPANY 

1910 


COPYRIGHT,  1866,  1898, 
BY  D.  APPLETON  AND  COMPANY. 


307 


PREFACE          ' 
TO  THE  REVISED  AND  ENLARGED  EDITION. 


KAPID  in  all  directions,  scientific  progress  has  during 
the  last  generation  been  more  rapid  in  the  direction  of 
Biology  than  in  any  other;  and  had  this  work  been  one 
dealing  with  Biology  at  large,  the  hope  of  bringing  it  up  to 
date  could  not  have  been  rationally  entertained.  But  it  is  a 
work  on  the  Principles  of  Biology ;  and  to  bring  an  expo- 
sition of  these  up  to  date,  seemed  not  impossible  with  such 
small  remnant  of  energy  as  is  left  me.  Slowly,  and  often 
interrupted  by  ill-health,  I  have  in  the  course  of  the  last 
two  years,  completed  this  first  volume  of  the  final  edition. 

Numerous  additions  have  proved  needful.  What  was 
originally  said  about  vital  changes  of  matter  has  been  sup- 
plemented by  a  chapter  on  "  Metabolism."  Under  the  title 
"  The  Dynamic  Element  in  Life,"  I  have  added  a  chapter 
which  renders  less  inadequate  the  conception  of  Life  pre- 
viously expressed.  A  gap  in  preceding  editions,  which 
should  have  been  occupied  by  some  pages  on  "  Structure," 
is  now  filled  up.  Those  astonishing  actions  in  cell-nuclei 
which  the  microscope  has  of  late  revealed,  will  be  found 
briefly  set  forth  under  the  head  of  "  Cell-Life  and  Cell- 
Multiplication."  Further  evidence  and  further  thought 
have  resulted  in  a  supplementary  chapter  on  "Genesis, 
Heredity,  and  Variation " ;  in  which  certain  views  enun- 


y 


537*5    550826 


vi  PREFACE  TO  THE  REVISED  EDITION. 

oiatcd  in  the  first  edition  are  qualified  and  developed. 
Various  modern  ideas  are  considered  under  the  title  "  Ke- 
cent  Criticisms  and  Hypotheses."  And  the  chapter  on 
"  The  Arguments  from  Embryology  "  has  been  mainly  re- 
written. Smaller  increments  have  taken  the  shape  of  new 
sections  incorporated  in  pre-existing  chapters.  They  are 
distinguished  by  the  following  section-marks : — §  8#,  §  46a, 
§  8fcz,  §  1000,  §  113a,  §  127a,  §§  130a— I30d.  There 
should  also  be  mentioned  a  number  of  foot-notes  of  some 
significance  not  present  in  preceding  editions.  Of  the 
three  additional  appendices  the  two  longer  ones  have  al- 
ready seen  the  light  in  other  shapes. 

After  these  chief  changes  have  now  to  be  named  the 
changes  necessitated  by  revision.  In  making  them  assist- 
ance has  been  needful.  Though  many  of  the  amendments 
have  resulted  from  further  thought  and  inquiry,  a  much 
larger  number  have  been  consequent  on  criticisms  received 
from  gentlemen  whose  aid  I  have  been  fortunate  enough  to 
obtain :  each  of  them  having  taken  a  division  falling  within 
the  range  of  his  special  studies.  The  part  concerned  with 
Organic  Chemistry  and  its  derived  subjects,  has  been  looked 
through  by  Mr.  W.  H.  Perkin,  Ph.D.,  F.R.S.,  Professor 
of  Organic  Chemistry,  Owens  College,  Manchester.  Plant 
Morphology  and  Physiology  have  been  overseen  by  Mr. 
A.  G.  Tansley,  M.A.,  F.L.S.,  Assistant  Professor  of  Bot- 
any, University  College,  London.  Criticisms  upon  parts 
dealing  with  Animal  Morphology,  I  owe  to  Mr.  E.  W.  Mac- 
Bride,  M.A.,  Fellow  of  St.  John's  College,  Cambridge,  Pro- 
fessor of  Zoology  in  the  McGill  University,  Montreal,  and 
Mr.  J.  T.  Cunningham,  M.A.,  late  Fellow  of  University 


PREFACE  TO  THE  REVISED  EDITION.  vij 

College,  Oxford.  And  the  statements  included  under  Ani- 
mal Physiology  have  been  checked  by  Mr.  W.  B.  Hardy, 
M.A.,  Fellow  of  Gonville  and  Cams  College,  Cambridge, 
Demonstrator  of  Physiology  in  the  University.  Where  the 
discoveries  made  since  1864  have  rendered  it  needful  to 
change  the  text,  either  by  omissions  or  qualifications  or  in 
some  cases  by  additions,  these  gentlemen  have  furnished 
me  with  the  requisite  information. 

Save  in  the  case  of  the  preliminary  portion,  bristling 
with  the  technicalities  of  Organic  Chemistry  (including  the 
pages  on  "  Metabolism  "),  I  have  not  submitted  the  proofs, 
either  of  the  new  chapters  or  of  the  revised  chapters,  to  the 
gentlemen  above  named.  The  abstention  has  resulted 
partly  from  reluctance  to  trespass  on  their  time  to  a  greater 
extent  than  was  originally  arranged,  and  partly  from  the 
desire  to  avoid  complicating  my  own  work.  During  the 
interval  occupied  in  the  preparation  of  this  volume  the 
printers  have  kept  pace  with  me,  and  I  have  feared  adding 
to  the  entailed  attention  the  further  attention  which  corre- 
spondence and  discussion  would  have  absorbed :  feeling  that 
it  was  better  to  risk  minor  inaccuracies  than  to  leave  the 
volume  unfinished :  an  event  which  at  one  time  appeared 
probable.  I  make  this  statement  because,  in  its  absence, 
one  or  other  of  these  gentlemen  might  be  held  responsible 
for  some  error  which  is  not  his  but  mine. 

Yet  another  explanation  is  called  for.  Beyond  the  ex- 
position of  those  general  truths  constituting  the  Principles 
of  Biology  as  commonly  accepted,  the  original  edition  of 
this  work  contained  sundry  views  for  which  biological 
opinion  did  not  furnish  any  authority.  Some  of  these  have 


viii  PREFACE  TO  THE  REVISED  EDITION. 

since  obtained  a  certain  currency ;  either  in  their  original 
forms  or  in  modified  forms.  Misinterpretations  are  likely 
to  result.  Readers  who  have  met  with  them  in  other  works 
may,  in  the  absence  of  warning,  suppose,  to  my  disadvan- 
tage, that  I  have  adopted  them  without  acknowledgment. 
Hence  it  must  be  understood  that  where  no  indication  to 
the  contrary  is  given  the  substance  is  unchanged.  Be- 
yond the  corrections  which  have  been  made  in  the  original 
text,  there  are,  in  some  cases,  additions  to  the  evidence  or 
amplifications  of  the  argument;  but  in  all  sections  not 
marked  as  new,  the  essential  ideas  set  forth  are  the  same  as 
they  were  in  the  original  edition  of  1864. 

BRIGHTON, 

August,  1898. 


PKEFACE. 


THE  aim  of  this  work  is  to  set  forth  the  general  truths  of 
Biology,  as  illustrative  of,  and  as  interpreted  by,  the  laws 
of  Evolution:  the  special  truths  being  introduced  only  so 
far  as  is  needful  for  elucidation  of  the  general  truths. 

For  aid  in  executing  it,  I  owe  many  thanks  to  Prof. 
Huxley  and  Dr.  Hooker.  They  have  supplied  me  with  in- 
formation where  my  own  was  deficient ;  *  and,  in  looking 
through  the  proof-sheets,  have  pointed  out  errors  of  detail 
into  which  I  had  fallen.  By  having  kindly  rendered  me 
this  valuable  assistance,  they  must  not,  however,  be  held 
committed  to  any  of  the  enunciated  doctrines  that  are  not 
among  the  recognized  truths  of  Biology. 

The  successive  instalments  which  compose  this  volume, 
were  issued  to  the  subscribers  at  the  following  dates: — No. 
7  (pp.  1—80)  in  January,  1863;  No.  8  (pp.  81—160)  in 
April,  1863;  No.  9  (pp.  161—240)  in  July,  1863;  No.  10 
(pp.  241—320)  in  January,  1864;  No.  11  (pp.  321 — 400)  in 
May,  1864;  and  No.  12  (pp.  401 — 476)  in  October,  1864. 
London,  September  2QM,  1864. 

*  Gross  misrepresentations  of  this  statement,  which  have  been  from  time 
to  time  made,  oblige  me,  much  against  my  will,  to  add  here  an  explanation  of 
it.  The  last  of  these  perversions,  uttered  in  a  lecture  delivered  at  Belfast  by 
the  Rev.  Professor  Watts,  D.D.,  is  reported  in  the  Belfast  Witness  of  Decem- 
ber 18, 1874 ;  just  while  ft  third  impression  of  thia  work  is  being  printed  from 

iz 


x  PREFACE. 

the  plates.  The  report  commences  as  follows : — "  Dr.  Watts,  after  showing 
that  on  his  own  confession  Spencer  was  indebted  for  his  facts  to  Huxley  and 
Hooker,  who,"  &c.,  &c. 

Wishing  in  this,  as  in  other  cases,  to  acknowledge  indebtedness  when  con 
scious  of  it,  I  introduced  the  words  referred  to,  in  recognition  of  the  fact  that 
I  had  repeatedly  questioned  the  distinguished  specialists  named,  on  matters 
beyond  my  knowledge,  which  were  not  dealt  with  in  the  books  at  my  com- 
mand. Forgetting  the  habits  of  antagonists,  and  especially  theological  antag- 
onists, it  never  occurred  to  me  that  my  expression  of  thanks  to  my  friends  for 
"  information  where  my  own  was  deficient,"  would  be  turned  into  the  sweep- 
ing statement  that  I  was  indebted  to  them  for  my  facts. 

Dad  Professor  Watts  looked  at  the  preface  to  the  second  volume  (the  two 
having  been  published  separately,  as  the  prefaces  imply),  he  would  have  seen 
a  second  expression  of  my  indebtedness  "  for  their  valuable  criticisms,  and 
for  the  trouble  they  have  taken  in  checking  the  numerous  statements  of  fact 
on  which  the  arguments  proceed  " — no  further  indebtedness  being  named.  A 
moment's  comparison  of  the  two  volumes  in  respect  of  their  accumulations 
of  facts,  would  have  shown  him  what  kind  of  warrant  there  was  for  his  inter- 
pretation. 

Doubtless  the  Rev.  Professor  was  prompted  to  make  this  assertion  by  the 
desire  to  discredit  the  work  he  was  attacking ;  and  having  so  good  an  end  in 
view,  thought  it  needless  to  be  particular  about  the  means.  In  the  art  of 
dealing  with  the  language  of  opponents,  Dr.  Watts  might  give  lessons  to 
Monsignor  Capel  and  Archbishop  Manning. 

December  28<A,  1874. 


CONTENTS   OF   VOL.  I. 


PART  I.— THE  DATA  OF.  BIOLOGY. 

CHAP.  PAOB! 

I. — ORGANIC  MATTER „,,.        .        3 

II. — THE  ACTIONS  OF  FORCES  ON  ORGANIC  MATTER        ....      27 

III. — THE   RE-ACTIONS   OF   ORGANIC    MATTER    ON   FORCES   ....         45 

III*. — METABOLISM 62 

IV. — PROXIMATE  CONCEPTION  OF  LIFE    .         .        .        .    .     .'  _,     .        .       78 

V. — THE   CORRESPONDENCE    BETWEEN   LIFE    AND   ITS    CIRCUMSTANCES  .         91 

VI. THE    DEGREE    OF    LIFE     VARIES     AS     THE    DEGREE     OF     CORRESPOND- 
ENCE      .  .       .       .       .       .    _ ,      f       .101 

VI\ — THE    DYNAMIC    ELEMENT   IN    LIFE      .  .  .  .  .  ,  .111 

VII.— THE  SCOPE  OF  BIOLOGY         .        .        .        .        .        .        .•       .     124 

PART  IL— THE  INDUCTIONS   OF  BIOLOGY. 

I.— GROWTH      .        .        .        . 135 

II.— DEVELOPMENT      .        .        .        .  .        .        .        .        .162 

II\ — STRUCTURE ' .        ,        .181 

III. — FUNCTION 197 

IV. — WASTE  AND  REPAIR 213 

V.— ADAPTATION        .         .        .       ...        .•     '  .^      ,        .227 

VI. — INDIVIDUALITY «        .        .        .        .     244 

VI\ — CELL-LIFE  AND  CELL-MULTIPLICATION 252 

VII. — GENESIS      i        ;    ' 269 

VIII.— HEREDITY 301 

IX. — VARIATION 320 

X. — GENESIS,  HEREDITY,  AND  VARIATION 336 

xi 


xii 


CONTENTS. 


C«AP. 
X\— GENESIS,    HEREDITY,    AND    VARIATION—  Concluded    .  .  .  .366 

XI.— CLASSIFICATION 374 

XII.— DISTRIBUTION 396 

PART  III.— THE  EVOLUTION  OF  LIFE. 

I.— PRELIMINARY     .        .        .        .  ,     .        .        .        .        .        .416 

II.— GENERAL  ASPECTS  or  THE  SPECIAL-CREATION-HYPOTHESIS     .        .417 

HI. GENERAL  ASPECTS  or  THE  EVOLUTION-HYPOTHESIS        .        .        .  431 

IV.— THE   ARGUMENTS   FROM    CLASSIFICATION 441 

y. — THE  ARGUMENTS  FROM  EMBRYOLOGY    .        .        .        .        .        .  460 

VI.— THE    ARGUMENTS   FROM    MORPHOLOGY 468 

VII. — THE    ARGUMENTS    FROM    DISTRIBUTION 476 

VIII.— HOW    IS   ORGANIC    EVOLUTION    CAUSED? 490 

IX.— EXTERNAL  FACTORS 499 

X. — INTERNAL  FACTORS 608 

XI.— DIRECT  EQUILIBRATION 519 

XII.— INDIRECT  EQUILIBRATION 629 

XIII. — THE    CO-OPERATION    OF    THE    FACTORS 649 

XIV. — THE    CONVERGENCE    OF   THE    EVIDENCES 654 

XIV*. — RECENT  CRITICISMS  AND  HYPOTHESES 559 

APPENDICES. 

A.— THE  GENERAL  LAW  OF  ANIMAL  FERTILITY 677 

B. — THE  INADEQUACY  OF  NATURAL  SELECTION,  ETC.  ....  602 
C.— THE  INHERITANCE  OF  FUNCTIONALLY-WROUGHT  MODIFICATIONS:  A 

SUMMARY 692 

D.— ON  ALLEGED  "  SPONTANEOUS  GENERATION  "  AND  ON  THE  HYPOTHESIS 

OF   PHYSIOLOGICAL    UNITS                                                                                   .            .  696 


PART  I. 

THE   DATA   OF   BIOLOGY. 


CHAPTER  I. 

ORGANIC    MATTER. 

§  1.  OF  the  four  chief  elements  which,  in  various  com- 
binations, make  up  living  bodies,  three  are  gaseous  under 
all  ordinary  conditions  and  the  fourth  is  a  solid.  Oxygen, 
hydrogen,  and  nitrogen  are  gases  which  for  many  years  defied 
all  attempts  to  liquefy  them,  and  carbon  is  a  solid  except 
perhaps  at  the  extremely  high  temperature  of  the  electric  arc. 
Only  by  intense  pressures  joined  with  extreme  refrigerations 
have  the  three  gases  been  reduced  to  the  liquid  form.*  There 
is  much  significance  in  this.  When  we  remember  how  those 
redistributions  of  Matter  and  Motion  which  constitute  Evo- 
lution, structural  and  functional,  imply  motions  in  the  units 
that  are  redistributed;  we  shall  see  a  probable  meaning  in 
the  fact  that  organic  bodies,  which  exhibit  the  phenomena 
of  Evolution  in  so  high  a  degree,  are  mainly  composed  of 
ultimate  units  having  extreme  mobility.  The  properties  of 
substances,  though  destroyed  to  sense  by  combination,  are 
not  destroyed  in  reality.  It  follows  from  the  persistence  of 
force,  that  the  properties  of  a  compound  are  resultants  of  the 
properties  of  its  components — resultants  in  which  the  pro- 
perties of  the  components  are  severally  in  full  action,  though 
mutually  obscured.  One  of  the  leading  properties  of  each 

*  In  this  passage  as  originally  written  (in  1862)  they  were  described  as 
incondensible ;  since,  though  reduced  to  the  density  of  liquids,  they  had  not 
been  liquefied. 

3 


4  THE  DATA  OP  BIOLOGY. 

substance  is  its  degree  of  molecular  mobility ;  and  its  degree 
of  molecular  mobility  more  or  less  sensibly  affects  the  molec- 
ular mobilities  of  the  various  compounds  into  which  it  enters. 
Hence  we  may  infer  some  relation  between  the  gaseous  form 
of  three  out  of  the  four  chief  organic  elements,  and  that 
comparative  readiness  displayed  by  organic  matters  to  un- 
dergo those  changes  in  the  arrangement  of  parts  which  we 
call  development,  and  those  transformations  of  motion  which 
we  call  function. 

Considering  them  chemically  instead  of  physically,  it  is  to 
be  remarked  that  three  out  of  these  four  main  components 
of  organic  matter,  have  affinities  which  are  narrow  in  their 
range  and  low  in  their  intensity.  Hydrogen,  it  is  true,  may 
be  made  to  combine  with  a  considerable  number  of  other  ele- 
ments ;  but  the  chemical  energy  which  it  -shows  is  scarcely  at 
all  shown  within  the  limits  of  the  organic  temperatures.  Of 
carbon  it  may  similarly  be  said  that  it  is  totally  inert  at  ordi- 
nary heats;  that  the  number  of  substances  with  which  it 
unites  is  not  great;  and  that  in  most  cases  its  tendency  to 
unite  with  them  is  but  feeble.  Lastly,  this  chemical  indiffer- 
ence is  shown  in  the  highest  degree  by  nitrogen — an  element 
which,  as  we  shall  hereafter  see,  plays  the  leading  part  in 
organic  changes. 

Among  the  organic  elements  (including  under  the  title 
not  only  the  four  chief  ones,  but  also  the  less  conspicuous  re- 
mainder), that  capability  of  assuming  different  states  called 
allotropism,  is  frequent.  Carbon  presents  itself  in  the  three 
unlike  conditions  of  diamond,  graphite,  and  charcoal.  Under 
certain  circumstances,  oxygen  takes  on  the  form  in  which  it 
is  called  ozone.  Sulphur  and  phosphorus  (both,  in  small 
proportions,  essential  constituents  of  organic  matter)  have 
allotropic  modifications.  Silicon,  too,  is  allotropic;  while  its 
oxide,  silica,  which  is  an  indispensable  constituent  of  many 
lower  organisms,  exhibits  the  analogue  of  allotropism — iso- 
merism.  No  other  interpretation  being  possible  we  are 
obliged  to  regard  allotropic  change  as  some  change  of  molecular 


ORGANIC  MATTER.  5 

arrangement.  Hence  this  frequency  of  its  occurrence  among 
the  components  of  organic  matter  is  significant  as  implying 
a  further  kind  of  molecular  mobility. 

One  more  fact,  that  is  here  of  great  interest  for  us,  must 
be  set  down.  These  four  elements  of  which  organisms  are 
almost  wholly  composed,  exhibit  certain  extreme  unlike- 
nesses.  While  between  two  of  them  we  have  an  unsurpassed 
contrast  in  chemical  activity;  between  one  of  them  and  the 
other  three,  we  have  an  unsurpassed  contrast  in  molecular 
mobility.  While  carbon,  until  lately  supposed  to  be  infusible 
and  now  volatilized  only  in  the  electric  arc,  shows  us  a  de- 
gree of  atomic  cohesion  greater  than  that  of  any  other  known 
element,  hydrogen,  oxygen,  and  nitrogen  show  the  least 
atomic  cohesion  of  all  elements.  And  while  oxygen  dis- 
plays, alike  in  the  range  and  intensity  of  its  affinities,  a 
chemical  energy  exceeding  that  of  any  other  substance  (un- 
less flourine  be  considered  an  exception),  nitrogen  displays 
the  greatest  chemical  inactivity.  Now  on  calling  to  mind 
one  of  the  general  truths  arrived  at  when  analyzing  the  pro- 
cess of  Evolution,  the  probable  significance  of  this  double 
difference  will  be  seen.  It  was  shown  (First  Principles, 
§  163)  that,  other  things  equal,  unlike  units  are  more  easily 
separated  by  incident  forces  than  like  units  are — that  an  in- 
cident force  falling  on  units  that  are  but  little  dissimilar 
does  not  readily  segregate  them;  but  that  it  readily  segre- 
gates them  if  they  are  widely  dissimilar.  Thus,  the  sub- 
stances presenting  these  two  extreme  contrasts,  the  one  be- 
tween physical  mobilities,  and  the  other  between  chemical 
activities,  fulfil,  in  the  highest  degree,  a  certain  further  con- 
dition to  facility  of  differentiation  and  integration. 

§  2.  Among  the  diatomic  combinations  of  the  three  ele- 
ments, hydrogen,  nitrogen  and  oxygen,  we  find  a  molecular 
mobility  much  less  than  that  of  these  elements  themselves ;  at 
the  same  time  that  it  is  much  greater  than  that  of  diatomic 
compounds  in  general.  Of  the  two  products  formed 

2 


6  THE  DATA  OF  BIOLOGY. 

by  the  union  of  oxygen  with  carbon,  the  first,  called  carbonic 
oxide,  which  contains  one  atom  *  of  carbon  to  one  of  oxygen 
(expressed  by  the  symbol  CO)  is  a  gas  condensible  only  with 
great  difficulty;  and  the  second,  carbonic  acid,  containing  an 
additional  atom  of  oxygen  (C  02)  assumes  a  liquid  form  also 
only  under  a  pressure  of  about  forty  atmospheres.  The 

several  compounds  of  oxygen  with  nitrogen,  present  us  with 
an  instructive  gradation.  Nitrous  oxide  (N"2  0),  is  a  gas 
condensible  only  under  a  pressure  of  some  fifty  atmospheres; 
nitric  oxide  (NO)  is  a  gas  which  although  it  has  been  lique- 
fied does  not  condense  under  a  pressure  of  270  atmospheres  at 
46.4°  F.  (8°  C.)  :  the  molecular  mobility  remaining  un- 
diminished  in  consequence  of  the  volume  of  the  united  gases 
remaining  unchanged.  Nitrogen  trioxide  (N2  03)  is  gaseous 
at  ordinary  temperatures,  but  condenses  into  a  very  volatile 
liquid  at  the  zero  of  Fahrenheit;  nitrogen  tetroxide  (N2  04) 
is  liquid  at  ordinary  temperatures  and  becomes  solid  at  the 
zero  of  Fahrenheit;  while  nitrogen  pentoxide  (N2  05)  may 
be  obtained  in  crystals  ^rhich  melt  at  85°  and  boil  at  113°. 
In  this  series  we  see,  though  not  with  complete  uniformity, 
a  decrease  of  molecular  mobility  as  the  weights  of  the  com- 
pound molecules  are  increased.  The  hydro-carbons 
illustrate  the  same  general  truth  still  better.  One  series  of 
them  will  suffice.  Marsh  gas  (C  H4)  is  gaseous  except  under 
great  pressure  and  at  very  low  temperatures.  Olefiant  gas 
(C2  H4)  and  ethane  (C,  He)  may  be  readily  liquefied  by  pres- 
sure. Propane  (C3  H8)  becomes  liquid  without  pressure  at 
the  zero  of  Fahrenheit.  Hexane  (C5  H12)  is  a  liquid  which 
boils  at  160°.  And  the  successively  higher  multiples,  heptane 
(C7H16),  octane  (C8H18),  and  nonane  (C9  H20)  are  liquids 
which  boil  respectively  at  210°,  257°,  and  302°.  Pentadecan 
(Ci5  H32)  is  a  liquid  which  boils  at  270°,  while  paraffin-wax, 

"Here  and  hereafter  the  word  "atom"  signifies  a  unit  of  something 
classed  as  an  element,  because  thus  far  undecomposed  by  us.  The  word  must 
not  be  supposed  to  mean  that  which  its  derivation  implies.  In  all  probability 
it  is  not  a  simple  unit  but  a  compound  one. 


ORGANIC  MATTER.  f 

which  contains  the  still  higher  multiples,  is  solid.  There 

are  three  compounds  of  hydrogen  and  nitrogen  that  have 
been  obtained  in  a  free  state — ammonia  (N  H3)  is  gaseous, 
but  liquefiable  by  pressure,  or  by  reducing  its  temperature 
to  —40°  F.,  and  it  solidifies  at  —112°  F. ;  hydrazine 
(NH2-NH2)is  liquid  at  ordinary  temperatures,  but  hydro- 
zoic  acid  (N3  H)  has  so  far  only  been  obtained  in  the  form  of 
a  highly  explosive  gas.  In  cyanogen,  which  is  composed 

of  carbon  and  nitrogen,  (C  N)2,  we  have  a  gas  that  becomes 
liquid  at  a  pressure  of  four  atmospheres  and  solid  at  — 30°  F. 
And  in  paracyanogen,  formed  of  the  same  proportions  of 
these  elements  in  higher  multiples,  we  have  a  solid  which  does 
not  fuse  or  volatilize  at  ordinary  temperatures.  Lastly, 

in  the  most  important  member  of  this  group,  water  (H2  0), 
we  have  a  compound  of  two  difficultly-condensible  gases  which 
assumes  both  the  fluid  state  and  the  solid  state  within  ordi- 
nary ranges  of  temperature;  while  its  molecular  mobility 
is  still  such  that  its  fluid  or  solid  masses  are  continually  pass- 
ing into  the  form  of  vapour,  though  not  with  great  rapidity 
until  the  temperature  is  raised  to  212°. 

Considering  them  chemically,  it  is  to  be  remarked  of  these 
diatomic  compounds  of  the  four  chief  organic  elements,  that 
they  are,  on  the  average,  less  stable  than  diatomic  compounds 
in  general.  Water,  carbonic  oxide,  and  carbonic  acid,  are, 
it  is  true,  difficult  to  decompose.  But  omitting  these,  the 
usual  strength  of  union  among  the  elements  of  the  above- 
named  substances  is  low  considering  the  simplicity  of  the 
substances.  With  the  exception  of  acetylene  and  possibly 
marsh  gas,  the  various  hydro-carbons  are  not  producible 
by  directly  combining  their  elements;  and  the  elements  of 
most  of  them  are  readily  separable  by  heat  without  the  aid 
of  any  antagonistic  affinity.  Nitrogen  and  hydrogen  do  not 
unite  with  each  other  immediately  save  under  very  excep- 
tional circumstances;  and  the  ammonia  which  results  from 
their  union,  though  it  resists  heat,  yields  to  the  electric 
spark.  Cyanogen  is  stable :  not  being  resolved  into  its  com- 


g  THE  DATA  OF  BIOLOGY. 

ponents  below  a  bright  red  heat.  Much  less  stable,  however, 
are  several  of  the  oxides  of  nitrogen.  Nitrous  oxide,  it  is 
true,  does  not  yield  up  its  elements  below  a  red  heat;  but 
nitrogen  tetroxide  cannot  exist  if  water  be  added  to  it; 
nitrous  acid  is  decomposed  by  water;  and  nitric  acid  not 
only  readily  parts  with  its  oxygen  to  many  metals,  but  when 
anhydrous,  spontaneously  decomposes.  Here  it  will 

be  well  to  note,  as  having  a  bearing  on  what  is  to  follow, 
how  characteristic  of  most  nitrogenous  compounds  is  this 
special  instability.  In  all  the  familiar  cases  of  sudden  and 
violent  decomposition,  the  change  is  due  to  the  presence  of 
nitrogen.  The  explosion  of  gunpowder  results  from  the 
readiness  with  which  the  nitrogen  contained  in  the  nitrate  of 
potash,  yields  up  the  oxygen  combined  with  it.  The  ex- 
plosion of  gun-cotton,  which  also  contains  nitrogen,  is  a  sub- 
stantially parallel  phenomenon.  The  various  fulminating 
salts  are  all  formed  by  the  union  with  metals  of  a  certain 
nitrogenous  acid  called  fulminic  acid;  which  is  so  unstable 
that  it  cannot  be  obtained  in  a  separate  state.  Explosive- 
ness  is  a  property  of  nitro-mannite,  and  also  of  mtro-glycerin. 
Iodide  of  nitrogen  detonates  on  the  slightest  touch,  and  often 
without  any  assignable  cause.  And  the  bodies  which  explode 
with  the  most  tremendous  violence  of  any  known,  are  the 
chloride  of  nitrogen  (X  C13)  and  hydrazoic  acid  (N"3H). 
Thus  these  easy  and  rapid  decompositions,  due  to  the  chemical 
indifference  of  nitrogen,  are  characteristic.  When  we  come 
hereafter  to  observe  the  part  which  nitrogen  plays  in  organic 
actions,  we  shall  see  the  significance  of  this  extreme  readiness 
shown  by  its  compounds  to  undergo  changes.  Keturn- 

ing  from  these  facts  parenthetically  introduced,  we  have  next 
to  note  that  though  among  the  diatomic  compounds  of  the 
four  chief  organic  elements,  there  are  a  few  active  ones,  yet 
the  majority  of  them  display  a  smaller  degree  of  chemical 
energy  than  the  average  of  diatomic  compounds.  Water  is 
the  most  neutral  of  bodies :  usually  producing  little  chemical 
alteration  in  the  substances  with  which  it  combines;  and 


ORGANIC  MATTER.  9 

being  expelled  from  most  of  its  combinations  by  a  moderate 
heat.  Carbonic  acid  is  a  relatively  feeble  acid:  the  carbon- 
ates being  decomposed  by  the  majority  of  other  acids  and  by 
ignition.  The  various  hydro-carbons  are  but  narrow  in  the 
range  of  their  comparatively  weak  affinities.  The  com- 
pounds formed  by  ammonia  have  not  much  stability:  they 
are  readily  destroyed  by  heat,  and  by  the  other  alkalies. 
The  affinities  of  cyanogen  are  tolerably  strong,  though  they 
yield  to  those  of  the  chief  acids.  Of  the  several  oxides  of 
nitrogen,  it  is  to  be  remarked  that,  while  those  containing 
the  smaller  proportions  of  oxygen  are  chemically  inert,  the 
one  containing  the  greatest  proportion  of  oxygen  (nitric  acid) 
though  chemically  active,  in  consequence  of  the  readiness 
with  which  one  part  of  it  gives  up  its  oxygen  to  oxidize  a 
base  with  which  the  rest  combines,  is  nevertheless  driven 
from  all  its  combinations  by  a  red  heat. 

These  diatomic  compounds,  like  their  elements,  are  to  a 
considerable  degree  characterized  by  the  prevalence  among 
them  of  allotropism ;  or,  as  it  is  more  usually  called  when  dis- 
played by  compound  bodies — isomerism.  Professor  Graham 
finds  reason  for  thinking  that  a  change  in  atomic  arrange- 
ments of  this  nature,  takes  place  in  water,  at  or  near  the 
melting  point  of  ice.  In  the  various  series  of  hydro-carbons, 
differing  from  each  other  only  in  the  ratios  in  which  the 
elements  are  united,  we  find  not  simply  isomerism  but  poly- 
merism  occurring  to  an  almost  infinite  extent.  In  some 
series  of  hydro-carbons,  as,  for  example,  the  terpenes,  we  find 
isomerism  and  at  the  same  time  a  great  tendency  to  undergo 
polymerisation.  And  the  relation  between  cyanogen  and 
paracyanogen  is,  as  we  saw,  a  polymeric  one. 

There  is  one  further  fact  respecting  these  diatomic  com- 
pounds of  the  chief  organic  elements,  which  must  not  be 
overlooked.  Those  of  them  which  form  parts  of  the  living 
tissues  of  plants  and  animals  (excluding  water  which  has  a 
mechanical  function,  and  carbonic  acid  which  is  a  product  of 
decomposition)  belong  for  the  most  part  to  one  group — the 


10  THE  DATA  OF   BIOLOGY. 

carbo-hydrates.*  And  of  this  group,  which  is  on  the  average 
characterized  by  comparative  instability  and  inertness,  these 
carbo-hydrates  found  in  living  tissues  are  among  the  most 
unstable  and  inert. 

§  3.  Passing  now  to  the  substances  which  contain  three  of 
these  chief  organic  elements,  we  have  first  to  note  that  along 
with  the  greater  atomic  weight  which  mostly  accompanies 
their  increased  complexity,  there  is,  on  the  average,  a  further 
marked  decrease  of  molecular  mobility.  Scarcely  any  of 
them  maintain  a  gaseous  state  at  ordinary  temperatures. 
One  class  of  them  only,  the  alcohols  and  their  derivatives, 
evaporate  under  the  usual  atmospheric  pressure;  but  not 
rapidly  unless  heated.  The  fixed  oils,  though  they  show 
that  molecular  mobility  implied  by  an  habitually  liquid  state, 
show  this  in  a  lower  degree  than  the  alcoholic  compounds; 
and  they  cannot  be  reduced  to  the  gaseous  state  without 
decomposition.  In  their  allies,  the  fats,  which  are  solid  unless 
heated,  the  loss  of  molecular  mobility  is  still  more  marked. 
And  throughout  the  whole  scries  of  the  fatty  acids,  in  which 
to  a  fixed  proportion  of  oxygen  there  are  successively  added 
higher  equimultiples  of  carbon  and  hydrogen,  we  see  how  the 
molecular  mobility  decreases  with  the  increasing  sizes  of  the 
molecules.  In  the  amylaceous  and  sugar-group  of  com- 
pounds, solidity  is  the  habitual  state:  such  of  them  as  can 
assume  the  liquid  form,  doing  so  only  when  heated  to  300° 
or  400°  F. ;  and  decomposing  when  further  heated,  rather 
than  become  gaseous.  Resins  and  gums  exhibit  general 
physical  properties  of  like  character  and  meaning. 

In  chemical  stability  these  triatomic  compounds,  consid- 
ered as  a  group,  are  in  a  marked  degree  below  the  diatomic 
ones.  The  various  sugars  and  kindred  bodies,  decompose  at  no 

*  The  name  hydro-carbons  was  here  used  when  these  pages  were  written, 
thirty-four  years  ago.  It  was  the  name  then  current.  In  this  case,  as  in 
multitudinous  other  cases,  the  substitution  of  newer  words  and  phrases  for 
older  ones,  is  somewhat  misleading.  Putting  the  thoughts  of  1862  in  the 
language  of  1897  gives  an  illusive  impression  of  recency. 


ORGANIC  MATTER.  H 

very  high  temperatures.  The  oils  and  fats  also  are  readily  car- 
bonized by  heat.  Resinous  and  gummy  substances  are  easily 
made  to  render  up  some  of  their  constituents.  And  the 
alcohols,  with  their  allies,  have  no  great  power  of  resisting 
decomposition.  These  bodies,  formed  by  the  union  of 

oxygen,  hydrogen,  and  carbon,  are  also,  as  a  class,  chemi- 
cally inactive.  Formic  and  acetic  are  doubtless  energetic 
acids;  but  the  higher  members  of  the  fatty-acid  series  are 
easily  separated  from  the  bases  with  which  they  combine. 
Saccharic  acid,  too,  is  an  acid  of  considerable  power;  and 
sundry  of  the  vegetable  acids  possess  a  certain  activity,  though 
an  activity  far  less  than  that  of  the  mineral  acids.  But 
throughout  the  rest  of  the  group,  there  is  shown  but  a  small 
tendency  to  combine  with  other  bodies;  and  such  combina- 
tions as  are  formed  have  usually  little  permanence. 

The  phenomena  of  isomerism  and  polymerism  are  of  fre- 
quent occurrence  in  these  triatomic  compounds.  Starch  and 
dextrine  are  probably  polymeric.  Fruit-sugar  and  grape- 
sugar,  mannite  and  sorbite,  cane-sugar  and  milk-sugar,  are 
isomeric.  Sundry  of  the  vegetal  acids  exhibit  similar  modi- 
fications. And  among  the  resins  and  gums,  with  their 
derivatives,  molecular  re-arrangements  of  this  kind  are  not 
uncommon. 

One  further  fact  respecting  these  compounds  of  carbon, 
oxygen  and  hydrogen,  should  be  mentioned;  namely,  that 
they  are  divisible  into  two  classes — the  one  consisting  of 
substances  that  result  from  the  destructive  decomposition  of 
organic  matter,  and  the  other  consisting  of  substances  that 
exist  as  such  in  organic  matter.  These  two  classes  of  sub- 
stances exhibit,  in  different  degrees,  the  properties  to  which 
we  have  been  directing  our  attention.  The  lower  alcohols, 
their  allies  and  derivatives,  which  possess  greater  molecular 
mobility  and  chemical  stability  than  the  rest  of  these  tri- 
atomic compounds,  are  rarely  found  in  animal  or  vegetal 
bodies.  While  the  sugars  and  amylaceous  substances,  the 
fixed  oils  and  fats,  the  gums  and  resins,  which  have  all  of 


13  THE  DATA  OP  BIOLOGY. 

them  much  less  molecular  mobility,  and  arc,  chemically  con- 
sidered,  more  unstable  and  inert,  are  components  of  the 
living  tissues  of  plants  and  animals. 

§4.  Among  compounds  containing  all  the  four  chief 
organic  elements,  a  division  analogous  to  that  just  named 
may  be  made.  There  are  some  which  result  from  the  decom- 
position of  living  tissues ;  there  are  others  which  make  parts 
of  living  tissues  in  their  state  of  integrity;  and  these  two 
groups  are  contrasted  in  their  properties  in  the  same  way  as 
are  the  parallel  groups  of  triatomic  compounds. 

Of  the  first  division,  certain  products  found  in  the  animal 
excretions  are  the  most  important,  and  the  only  ones  that 
need  be  noted;  such,  namely,  as  urea,  kreatine,  kreatinine. 
These  animal-bases  exhibit  much  less  molecular  mobility  than 
the  average  of  the  substances  treated  of  in  the  last  section : 
being  solid  at  ordinary  temperatures,  fusing,  where  fusible  at 
all,  at  temperatures  above  that  of  boiling  water,  and  having 
no  power  to  assume  a  gaseous  state.  Chemically  considered, 
their  stability  is  low,  and  their  activity  but  small,  in  com- 
parison with  the  stabilities  and  activities  of  the  simpler  com- 
pounds. 

It  is,  however,  the  nitrogenous  constituents  of  living  tis- 
sues, that  display  most  markedly  those  characteristics  of 
which  we  have  been  tracing  the  growth.  Albumen,  fibrin, 
casein,  and  their  allies,  are  bodies  in  which  that  molecular 
mobility  exhibited  by  three  of  their  components  in  so  high  a 
degree  is  reduced  to  a  minimum.  These  substances  are  known 
only  in  the  solid  state.  That  is  to  say,  when  deprived  of  the 
water  usually  mixed  with  them,  they  do  not  admit  of  fusion, 
much  less  of  volatilization  To  which  add,  that  they  have  not 
evtn  that  molecular  mobility  which  solution  in  water  implies ; 
since,  though  they  form  viscid  mixtures  with  water,  they  do 
not  dissolve  in  the  same  perfect  way  as  do  inorganic  com- 
pounds. The  chemical  characteristics  of  these  sub- 
stances are  instability  and  inertness  carried  to  the  extreme. 
How  rapidly  albumenoid  matters  decompose  under  ordinary 


ORGANIC  MATTER.  13 

conditions,  is  daily  seen:  the  difficulty  of  every  housewife 
being  to  prevent  them  from  decomposing.  It  is  true  that 
when  desiccated  and  kept  from  contact  with  air,  they  may  be 
preserved  unchanged  for  long  periods ;  but  the  fact  that  they 
can  be  only  thus  preserved,  proves  their  great  instability.  It 
is  true,  also,  that  these  most  complex  nitrogenous  principles 
are  not  absolutely  inert,  since  they  enter  into  combinations 
with  some  bases ;  but  their  unions  are  very  feeble. 

It  should  be  noted,  too,  of  these  bodies,  that  though  they 
exhibit  in  the  lowest  degree  that  kind  of  molecular  mobility 
which  implies  facile  vibration  of  the  molecules  as  wholes, 
they  exhibit  in  high  degrees  that  kind  of  molecular  mobility 
resulting  in  isomerism,  which  implies  permanent  changes  in 
the  positions  of  adjacent  atoms  with  respect  to  each  other. 
Each  of  them  has  a  soluble  and  an  insoluble  form.  In  some 
cases  there  are  indications  of  more  than  two  such  forms. 
And  it  appears  that  their  metamorphoses  take  place  under 
very  slight  changes  of  conditions. 

In  these  most  unstable  and  inert  organic  compounds,  we 
find  that  the  molecular  complexity  reaches  a  maximum :  not 
only  since  the  four  chief  organic  elements  are  here  united 
with  small  proportions  of  sulphur  and  sometimes  phosphorus ; 
but  also  since  they  are  united  in  high  multiples.  The 
peculiarity  which  we  found  characterized  even  diatomic  com- 
pounds of  the  organic  elements,  that  their  molecules  are 
formed  not  of  single  equivalents  of  each  component,  but  of 
two,  three,  four,  and  more  equivalents,  is  carried  to  the  great- 
est extreme  in  these  compounds,  which  take  the  leading 
part  in  organic  actions.  According  to  Lieberkiihn,  the  for- 
mula of  albumen  is  C72  H112  SN18  022.  That  is  to  say,  with 
the  sulphur  there  are  united  seventy-two  atoms  of  carbon, 
one  hundred  and  twelve  of  hydrogen,  eighteen  of  nitrogen, 
and  twenty-two  of  oxygen :  the  molecule  being  thus  made  up 
of  more  than  two  hundred  ultimate  atoms. 

§  5.  Did  space  permit,  it  would  be  useful  here  to  consider 
in  detail  the  interpretations  that  may  be  given  of  the  pecu- 


14  TRR  DATA  OP  BIOLOGY. 

liaritics  we  have  been  tracing:  bringing  to  their  solution, 
the  general  mechanical  principles  which  are  now  found  to 
hold  true  of  molecules  as  of  masses.  But  it  must  suffice 
briefly  to  indicate  the  conclusions  which  such  an  inquiry 
promises  to  bring  out. 

Proceeding  on  these  principles,  it  may  be  argued  that  the 
molecular  mobility  of  a  substance  must  depend  partly  on  the 
inertia  of  its  molecules;  partly  on  the  intensity  of  their 
mutual  polarities ;  partly  on  their  mutual  pressures,  as  deter- 
mined by  the  density  of  their  aggregation;  and  (where  the 
molecules  are  compound)  partly  on  the  molecular  mobilities 
of  their  component  molecules.  Whence  it  is  to  be  inferred 
that  any  three  of  these  remaining  constant,  the  molecular 
mobility  will  vary  as  the  fourth.  Other  things  equal,  there- 
fore, the  molecular  mobility  of  molecules  must  decrease  as 
their  masses  increase;  and  so  there  must  result  that  pro- 
gression we  have  traced,  from  the  high  molecular  mobility 
of  the  uncombined  organic  elements,  to  the  low  molecular 
mobility  of  those  large-moleculed  substances  into  which  they 
are  ultimately  compounded. 

Applying  to  molecules  the  mechanical  law  which  holds  of 
masses,  that  since  inertia  and  gravity  increase  as  the  cubes 
of  the  dimensions  while  cohesion  increases  as  their  squares, 
the  self-sustaining  power  of  a  body  becomes  relatively 
smaller  as  its  bulk  becomes  greater;  it  might  be  argued  that 
these  large,  aggregate  molecules  which  constitute  organic 
substances,  are  mechanically  weak — are  less  able  than  simpler 
molecules  to  bear,  without  alteration,  the  forces  falling  on 
them.  That  very  massiveness  which  renders  them  less  mo- 
bile, enables  the  physical  forces  acting  on  them  more  readily 
to  change  the  relative  positions  of  their  component  atoms; 
and  so  to  produce  what  we  know  as  re-arrangements  and  de- 
compositions. 

Further,  it  seems  a  not  improbable  conclusion,  that  this 
formation  of  large  aggregates  of  elementary  atoms  and  re- 
sulting diminution  of  self-sustaining  power,  must  be  accom- 


ORGANIC  MATTER.  15 

panied  by  a  decrease  of  those  dimensional  contrasts  to  which 
polarity  is  ascribable.  A  sphere  is  the  figure  of  equilibrium 
which  any  aggregate  of  units  tends  to  assume,  under  the 
influence  of  simple  mutual  attraction.  Where  the  number 
of  units  is  small  and  their  mutual  polarities  are  decided, 
this  proclivity  towards  spherical  grouping  will  be  overcome 
by  the  tendency  towards  some  more  special  form,  determined 
by  their  mutual  polarities.  But  it  is  manifest  that  in  pro- 
portion as  an  aggregate  molecule  becomes  larger,  the  effects 
of  simple  mutual  attraction  must  become  relatively  greater; 
and  so  must  tend  to  mask  the  effects  of  polar  attraction. 
There  will  consequently  be  apt  to  result  in  highly  compound 
molecules  like  these  organic  ones,  containing  hundreds  of 
elementary  atoms,  such  approximation  to  the  spherical  form 
as  must  involve  a  less  distinct  polarity  than  in  simpler  mole- 
cules. If  this  inference  be  correct,  it  supplies  us  with  an  ex- 
planation both  of  the  chemical  inertness  of  these  most  com- 
plex organic  substances,  and  of  their  inability  to  crystallize. 

§  6.  Here  we  are  naturally  introduced  to  another  aspect  of 
our  subject — an  aspect  of  great  interest.  Professor  Graham 
has  published  a  series  of  important  researches,  which  promise 
to  throw  much  light  on  the  constitution  and  changes  of 
organic  matter.  He  shows  that  solid  substances  exist  under 
two  forms  of  aggregation — the  colloid  or  jelly-like,  and  the 
crystalloid  or  crystal-like.  Examples  of  the  last  are  too 
familiar  to  need  specifying.  Of  the  first  may  be  named  such 
instances  as  "  hydrated  silicic  acid,  hydrated  alumina,  and 
other  metallic  peroxides  of  the  aluminous  class,  when  they 
exist  in  the  soluble  form;  with  starch,  dextrine  and  the 
gums,  caramel,  tannin,  albumen,  gelatine,  vegetable  and 
animal  extractive  matters."  Describing  the  properties  of 
colloids,  Professor  Graham  says : — "  Although  often  largely 
soluble  in  water,  they  are  held  in  solution  by  a  most  feeble 
force.  They  appear  singularly  inert  in  the  capacity  of  acids 
and  bases,  and  in  all  the  ordinary  chemical  relations." 


jg  THE  DATA  OP  BIOLOGY. 

*  *  *  "  Although  chemically  inert  in  the  ordinary  sense, 
colloids  possess  a  compensating  activity  of  their  own  arising 
out  of  their  physical  properties.  While  the  rigidity  of  the 
crystalline  structure  shuts  out  external  impressions,  the  soft- 
ness of  the  gelatinous  colloid  partakes  of  fluidity,  and  enables 
the  colloid  to  become  a  medium  of  liquid  diffusion,  like  water 
itself."  *  *  *  "  Hence  a  wide  sensibility  on  the  part  of 
colloids  to  external  agents.  Another  and  eminently  charac- 
teristic quality  of  colloids  is  their  mutability."  *  *  *  "The 
solution  of  hydrated  silicic  acid,  for  instance,  is  easily  ob- 
tained in  a  state  of  purity,  but  it  cannot  be  preserved.  It  may 
remain  fluid  for  days  or  weeks  in  a  sealed  tube,  but  is  sure  to 
gelatinize  and  become  insoluble  at  last.  Nor  does  the  change 
of  this  colloid  appear  to  stop  at  that  point;  for  the  mineral 
forms  of  silicic  acid,  deposited  from  water,  such  as  flint,  are 
often  found  to  have  passed,  during  the  geological  ages  of 
their  existence,  from  the  vitreous  or  colloidal  into  the  crys- 
talline condition  (II.  Rose).  The  colloid  is,  in  fact,  a  dyna- 
mical state  of  matter,  the  crystalloidal  being  the  statical 
condition.  The  colloid  possesses  energia.  It  may  be  looked 
upon  as  the  primary  source  of  the  force  appearing  in  the 
phenomena  of  vitality.  To  the  gradual  manner  in  which 
colloidal  changes  take  place  (for  they  always  demand  time  as 
an  element)  may  the  characteristic  protraction  of  chemico- 
organic  changes  also  be  referred." 

The  class  of  colloids  includes  not  only  all  those  most  com- 
plex nitrogenous  compounds  characteristic  of  organic  tissues, 
and  sundry  of  the  carbo-hydrates  found  along  with  them; 
but,  significantly  enough,  it  includes  several  of  those  sub- 
stances classed  as  inorganic,  which  enter  into  organized 
structures.  Thus  silica,  which  is  a  component  of  many 
plants,  and  constitutes  the  spicules  of  sponges  as  well  as  the 
shells  of  many  foraminifera  and  infusoria,  has  a  colloid,  as 
well  as  a  crystalloid,  condition.  A  solution  of  hydrated  silicic 
acid  passes  in  the  course  of  a  few  days  into  a  solid  jelly  that 


ORGANIC  MATTER.  17 

is  no  longer  soluble  in  water;  and  it  may  be  suddenly  thus 
coagulated  by  a  minute  portion  of  an  alkaline  carbonate,  as 
well  as  by  gelatine,  alumina,  and  peroxide  of  iron.  This  last- 
named  substance,  too — peroxide  of  iron — which  is  an  ingre- 
dient in  the  blood  of  mammals  and  composes  the  shells  of 
certain  Protozoa,  has  a  colloid  condition.  "  Water  containing 
about  one  per  cent,  of  hydrated  peroxide  of  iron  in  solution, 
has  the  dark  red  colour  of  venous  blood."  *  *  *  "  The 
red  solution  is  coagulated  in  the  cold  by  traces  of  sulphuric 
acid,  alkalies,  alkaline  carbonates,  sulphates,  and  neutral  salts 
in  general."  *  *  *  "  The  coagulum  is  a  deep  red-coloured 
jelly,  resembling  the  clot  of  blood,  but  more  transparent. 
Indeed,  the  coagulum  of  this  colloid  is  highly  suggestive 
of  that  of  blood,  from  the  feeble  agencies  which  suffice  to 
effect  the  change  in  question,  as  well  as  from  the  appearance 
of  the  product."  The  jelly  thus  formed  soon  becomes,  like 
the  last,  insoluble  in  water.  Lime  also,  which  is  so  important 
a  mineral  element  in  living  bodies,  animal  and  vegetal, 
enters  into  a  compound  belonging  to  this  class.  "  The 
well-known  solution  of  lime  in  sugar  forms  a  solid  coagulum 
when  heated.  It  is  probably,  at  a  high  temperature,  entirely 
colloidal." 

Generalizing  some  of  the  facts  which  he  gives,  Professor 
Graham  says: — "The  equivalent  of  a  colloid  appears  to  be 
always  high,  although  the  ratio  between  the  elements  of  the 
substance  may  be  simple.  Gummic  acid,  for  instance,  may 
be  represented  by  C12  H22  O11 ;  but,  judging  from  the  small 
proportions  of  lime  and  potash  which  suffice  to  neutralize  this 
acid,  the  true  numbers  of  its  formula  must  be  several  times 
greater.  It  is  difficult  to  avoid  associating  the  inertness  of 
colloids  with  their  high  equivalents,  particularly  where  the 
high  number  appears  to  be  attained  by  the  repetition  of  a 
small  number.  The  inquiry  suggests  itself  whether  the 
colloid  molecule  may  not  be  constituted  by  the  grouping 
together  of  a  number  of  smaller  crystalloid  molecules,  and 


18  THE  DATA  OF  BIOLOGY. 

whether  the  basis  of  colloidality  may  not  really  be  this  com- 
posite character  of  the  molecule." 

§  7.  A  further  contrast  between  colloids  and  crystalloids 
is  equally  significant  in  its  relations  to  vital  phenomena. 
Professor 'Graham  points  out  that  the  marked  differences  in 
volatility  displayed  by  different  bodies,  are  paralleled  by  dif- 
ferences in  the  rates  of  diffusion  of  different  bodies  through 
liquids.'  As  alcohol  and  ether  at  ordinary  temperatures,  and 
various  other  substances  at  higher  temperatures,  diffuse  them- 
selves in  a  gaseous  form  through  the  air;  so,  a  substance  in 
aqueous  solution,  when  placed  in  contact  with  a  mass  of 
water  (in  such  way  as  to  avoid  mixture  by  circulating 
currents)  diffuses  itself  through  this  mass  of  water.  And 
just  as  there  are  various  degrees  of  rapidity  in  evaporation, 
so  there  are  various  degrees  of  rapidity  in  diffusion:  "the 
range  also  in  the  degree  of  diffusive  mobility  exhibited  by 
different  substances  appears  to  be  as  wide  as  the  scale  of 
vapour-tensions."  This  parallelism  is  what  might  have  been 
looked  for;  since  the  tendency  to  assume  a  gaseous  state, 
and  the  tendency  to  spread  in  solution  through  a  liquid,  are 
both  consequences  of  molecular  mobility.  It  also  turns  out, 
as  was  to  be  expected,  that  diffusibility,  like  volatility,  has, 
other  things  equal,  a  relation  to  molecular  weight — other 
things  equal,  we  must  say,  because  molecular  mobility  must, 
as  pointed  out  in  §  5,  be  affected  by  other  properties  of 
atoms,  besides  their  inertia.  Thus  the  substance  most 
rapidly  diffused  of  any  on  which  Professor  Graham  experi- 
mented, was  hydrochloric  acid — -a  compound  which  is  of 
low  molecular  weight,  is  gaseous  save  under  a  pressure  of 
forty  atmospheres,  and  ordinarily  exists  as  a  liquid,  only  in 
combination  with  water.  Again,  "hydrate  of  potash  may 
be  said  to  possess  double  the  velocity  of  diffusion  of  sulphate 
of  potash,  and  sulphate  of  potash  again  double  the  velocity 
of  sugar,  alcohol,  and  sulphate  of  magnesia," — differences 


ORGANIC  MATTER.  19 

which  have  a  general  correspondence  with  differences  in  the 
massiveness  of  their  molecules. 

But  the  fact  of  chief  interest  to  us  here,  is  that  the  rela- 
tively small-moleculed  crystalloids  have  immensely  greater 
diffusive  power  than  the  relatively  large-moleculed  colloids. 
Among  the  crystalloids  themselves  there  are  marked  differ- 
ences of  diffusibility;  and  among  the  colloids  themselves 
there  are  parallel  differences,  though  less  marked  ones.  But 
these  differences  are  small  compared  with  that  between  the 
diffusibility  of  the  crystalloids  as  a  class,  and  the  diffusibility 
of  the  collloids  as  a  class.  Hydrochloric  acid  is  seven  times 
as  diffusible  as  sulphate  of  magnesia;  but  it  is  fifty  times 
as  diffusible  as  albumen,  and  a  hundred  times  as  diffusible  as 
caramel. 

These  differences  of  diffusibility  manifest  themselves  with 
nearly  equal  distinctness,  when  a  permeable  septum  is  placed 
between  the  solution  and  the  water.  The  result  is  that 
when  a  solution  contains  substances  of  different  diffusibilities, 
the  process  of  dialysis,  as  Professor  Graham  calls  it,  becomes 
a  means  of  separating  the  mixed  substances :  especially  when 
such  mixed  substances  are  partly  crystalloids  and  partly  col- 
loids. The  bearing  of  this  fact  on  the  interpretation  of 
organic  processes  will  be  obvious.  Still  more  obvious 

will  its  bearing  be,  on  joining  with  it  the  remarkable  fact 
that  while  crystalloids  can  diffuse  themselves  through  colloids 
nearly  as  rapidly  as  through  water,  colloids  can  scarcely 
diffuse  themselves  at  all  through  other  colloids.  From  a 
mass  of  jelly  containing  salt,  into  an  adjoining  mass  of  jelly 
containing  no  salt,  the  salt  spread  more  in  eight  days  than  it 
spread  through  water  in  seven  days;  while  the  spread  of 
"  caramel  through  the  jelly  appeared  scarcely  to  have  begun 
after  eight  days  had  elapsed."  So  that  we  must  regard  the 
colloidal  compounds  of  which  organisms  are  built,  as  having, 
by  their  physical  nature,  the  ability  to  separate  colloids  from 
crystalloids,  and  to  let  the  crystalloids  pass  through  them 
with  scarcely  any  resistance. 


20  THE  DATA  OP  BIOLOGY. 

One  other  result  of  these  researches  on  the  relative  diffusi- 
bilities  of  different  substances  has  a  meaning  for  us.  Pro- 
fessor Graham  finds  that  not  only  does  there  take  place,  by 
dialysis,  a  separation  of  mixed  substances  which  are  unlike  in 
their  molecular  mobilities ;  but  also  that  combined  substances 
between  which  the  affinities  are  feeble,  will  separate  on  the 
dialyzer,  if  their  molecular  mobilities  are  strongly  con- 
trasted. Speaking  of  the  hydrochloride  of  peroxide  of  iron, 
he  says,  "  such  a  compound  possesses  an  element  of  in- 
stability in  the  extremely  unequal  diffusibility  of  its  con- 
stituents ; "  and  he  points  out  that  when  dialyzed,  the 
hydrochloric  acid  gradually  diffuses  away,  leaving  the  col- 
loidal peroxide  of  iron  behind.  Similarly,  he  remarks  of 
the  peracetate  of  iron,  that  it  "  may  be  made  a  source  of 
soluble  peroxide,  as  the  salt  referred  to  is  itself  decomposed 
to  a  great  extent  by  diffusion  on  the  dialyzer."  Now  this 
tendency  to  separate  displayed  by  substances  which  differ 
widely  in  their  molecular  mobilities,  though  usually  so 
far  antagonized  by  their  affinities  as  not  to  produce  spon- 
taneous decomposition,  must,  in  all  cases,  induce  a  certain 
readiness  to  change  which  would  not  else  exist.  The  un- 
equal mobilities  of  the  combined  atoms  must  give  disturbing 
forces  a  greater  power  to  work  transformations  than  they 
would  otherwise  have.  Hence  the  probable  significance  of  a 
fact  named  at  the  outset,  that  while  three  of  the  chief  organic 
elements  have  the  greatest  atomic  mobilities  of  any  elements 
known,  the  fourth,  carbon,  has  the  least  atomic  mobility  of 
known  elements.  Though,  in  its  simple  compounds,  the 
affinities  of  carbon  for  the  rest  are  strong  enough  to  prevent 
the  effects  of  this  great  difference  from  clearly  showing  them- 
selves; yet  there  seems  reason  to  think  that  in  those  com- 
plex compounds  composing  organic  bodies — compounds  in 
which  there  are  various  cross  affinities  leading  to  a  state 
of  chemical  tension — this  extreme  difference  in  the  molecular 
mobilities  must  be  an  important  aid  to  molecular  re-arrange- 
ments. In  short,  we  are  here  led  by  concrete  evidence  to  the 


ORGANIC  MATTER.  21 

conclusion  which  we  before  drew  from  first  principles,  that 
this  great  imlikeness  among  the  combined  units  must  facili- 
tate differentiations. 

§  8.  A  portion  of  organic  matter  in  a  state  to  exhibit 
those  phenomena  which  the  biologist  deals  with,  is,  however, 
something  far  more  complex  than  the  separate  organic  mat- 
ters we  have  been  studying ;  since  a  portion  of  organic  matter 
in  its  integrity,  contains  several  of  these. 

In  the  first  place  no  one  of  those  colloids  which  make  up 
the  mass  of  a  living  body,  appears  capable  of  carrying  on 
vital  changes  by  itself:  it  is  always  associated  with  other 
colloids.  A  portion  of  animal-tissue,  however  minute,  almost 
always  contains  more  than  one  form  of  protein-substance: 
different  chemical  modifications  of  albumen  and  gelatine  are 
present  together,  as  well  as,  probably,  a  soluble  and  insoluble 
modification  of  each;  and  there  is  iisually  more  or  less  of 
fatty  matter.  In  a  single  vegetal  cell,  the  minute  quantity 
of  nitrogenous  colloid  present,  is  imbedded  in  colloids  of  the 
non-nitrogenous  class.  And  the  microscope  makes  it  at  once 
manifest,  that  even  the  smallest  and  simplest  organic  forms 
are  not  absolutely  homogeneous. 

Further,  we  have  to  contemplate  organic  tissue,  formed 
of  mingled  colloids  in  both  soluble  and  insoluble  states,  as 
permeated  throughout  by  crystalloids.  Some  of  these  crys- 
talloids, as  oxygen,*  water,  and  perhaps  certain  salts,  are 
agents  of  decomposition;  some,  as  the  saccharine  and  fatty 
matters,  are  probably  materials  for  decomposition ;  and  some, 
as  carbonic  acid,  water,  urea,  kreatine,  and  kreatinine,  are 
products  of  decomposition.  Into  the  mass  of  mingled  colloids, 
mostly  insoluble  and  where  soluble  of  very  low  molecular 
mobility  or  diffusive  power,  we  have  constantly  passing,  crys- 

*  It  will  perhaps  seem  strange  to  class  oxygen  as  a  crystalloid.     But  inas- 
much as  the  crystalloids  are  distinguished  from  the  colloids  by  their  atomic 
simplicity,  and  inasmuch  as  sundry  gases  are  reducible  to  a  crystalline  state, 
we  are  justified  in  so  classing  it. 
3 


22 


THE  DATA  OP  BIOLOGY. 


talloids  of  high  molecular  mobility  or  diffusive  power,  that 
are  capable  of  decomposing  these  complex  colloids,  or  of 
facilitating  decompositions  otherwise  caused;  and  from  these 
complex  colloids,  when  decomposed,  there  result  other  crys- 
talloids (the  two  chief  ones  extremely  simple  and  mobile,  and 
the  rest  comparatively  so)  which  diffuse  away  as  rapidly  as 
they  are  formed. 

And  now  we  may  clearly  see  the  necessity  for  that  pecu- 
liar composition  which  we  find  in  organic  matter.  On  the 
one  hand,  were  it  not  for  the  extreme  molecular  mobility 
possessed  by  three  out  of  the  four  of  its  chief  elements;  and 
were  it  not  for  the  consequently  high  molecular  mobility  of 
their  simpler  compounds ;  there  could  not  be  this  quick  escape 
of  the  waste  products  of  organic  action ;  and  there  could  not 
be  that  continuously  active  change  of  matter  which  vitality 
implies.  On  the  other  hand,  were  it  not  for  the  union  of 
these  extremely  mobile  elements  into  immensely  complex 
compounds,  having  relatively  vast  molecules  which  are  made 
comparatively  immobile  by  their  inertia,  there  could  not 
result  that  mechanical  fixity  which  prevents  the  components 
of  living  tissue  from  diffusing  away  along  with  the  effete 
matters  produced  by  decomposition. 

§  8a.  Let  us  not  omit  here  to  note  the  ways  in  which  the 
genesis  of  these  traits  distinguishing  organic  matter  con- 
forms to  the  laws  of  evolution  as  expressed  in  its  general 
formula. 

In  pursuance  of  the  belief  now  widely  entertained  by 
chemists  that  the  so-called  elements  are  not  elements,  but  are 
composed  of  simpler  matters  and  probably  of  one  ultimate 
form  of  matter  (for  which  the  name  "  protyle  "  has  been  sug- 
gested by  Sir  W.  Crookes),  it  is  to  be  concluded  that  the  for- 
mation of  the  elements,  in  common  with  the  formation  of  all 
those  compounds  of  them  which  Nature  presents,  took  place 
in  the  course  of  Cosmic  Evolution.  Various  reasons  for  this 
inference  the  reader  will  find  set  forth  in  the  Addenda  to  an 


ORGANIC  MATTER.  23 

essay  on  "  The  Nebular  Hypothesis "  (see  Essays,  vol.  I, 
p.  155).  On  tracing  out  the  process  of  compounding  and  re- 
compounding  by  which,  hypothetically,  the  elements  them- 
selves and  afterwards  their  compounds  and  re-compounds 
have  arisen,  certain  cardinal  facts  become  manifest. 

1.  Considered  as  masses,  the  units  of  the  elements  are  the 
smallest,  though   larger  than  the  units  of  the  primordial 
matter.     Later  than  these,  since  they  are  composed  of  them, 
and  since  they  cannot  exist  at  temperatures  so  high  as  those 
at  which  the  elements  can  exist,  come  the  diatomic  com- 
pounds— oxides,  chlorides,  and  the  rest — necessarily  larger  in 
their    molecules.      Above    these    in    massiveness    come    the 
molecules  of  the   multitudinous   salts   and   kindred   bodies. 
When  associated,  as  these  commonly  are,  with  molecules  of 
water,  there  again  results  in  each  case  increase  of  mass ;  and 
unable  as  they  are  to  bear  such  high  temperatures,  these 
molecules  are  necessarily  later  in  origin  than  those  of  the 
anhydrous  diatomic  compounds.      Within  the  general  class 
of    triatomic    compounds,    more    composite  still,    come    the 
carbo-hydrates,  which,  being  able  to  unite  in  multiples,  form 
still  larger  molecules  than  other  triatomic  compounds.     De- 
composing as  they  do  at  relatively  low  temperatures,  these 
are  still  more  recent  in  the  course  of  chemical  evolution ;  and 
with  the  genesis  of  them  the  way  is  prepared  for  the  genesis 
of   organic   matter   strictly    so    called.      This    includes    the 
various   forms   of   protein-substance,   containing   four   chief 
elements  with  two  minor  ones,  and  having  relatively  vast 
molecules.     Unstable  as  these  are  in  presence  of  heat  and 
surrounding  affinities,  they  became  possible  only  at  a  late 
stage  in  the  genesis  of  the  Earth.    Here,  then,  in  that  chemi- 
cal evolution  which  preceded  the  evolution  of  life,  we  see 
displayed  that  process  of  integration  which  is  the  primary 
trait  of  evolution  at  large. 

2.  Along  with  increasing  integration  has  gone  progress  in 
heterogeneity.     The  elements,  regarding  them  as  compound, 
are  severally  more  heterogeneous  than  "  protyle."    Diatomic 


24  THE  DATA  OP  BIOLOGY. 

molecules  are  more  heterogeneous  than  these  elements ;  tri- 
atomic  more  heterogeneous  than  diatomic ;  and  the  molecules 
containing  four  elements  more  heterogeneous  than  those  con- 
taining three:  the  most  heterogeneous  of  them  being  the 
proteids,  which  contain  two  other  elements.  The  hydrated 
forms  of  all  these  compounds  are  more  heterogeneous  than 
are  the  anhydrous  forms.  And  most  heterogeneous  of  all 
are  the  molecules  which,  besides  containing  three,  four,  or 
more  elements,  also  exhibit  the  isomerism  and  polymerism 
which  imply  unions  in  multiples. 

3.  This  formation  of  molecules  more  and  more  heteroge- 
neous during  terrestrial  evolution,  has  been  accompanied  by- 
increasing  heterogeneity  in  the  aggregate  of  compounds  of 
each  kind,  as  well  as  an  increasing  number  of  kinds;  and 
this  increasing  heterogeneity  is  exemplified  in  an  extreme 
degree  in  the  compounds,  non-nitrogenous  and  nitrogenous, 
out  of  which  organisms  are  built.  So  that  the  classes, 
orders,  genera,  and  species  of  chemical  substances,  gradually 
increasing  as  the  Earth  has  assumed  its  present  form,  in- 
creased in  a  transcendent  degree  during  that  stage  which 
preceded  the  origin  of  life. 

§  9.  Returning  now  from  these  partially-parenthetic  ob- 
servations, and  summing  up  the  contents  of  the  preceding 
pages,  we  have  to  remark  that  in  the  substances  of  which  or- 
ganisms are  composed,  the  conditions  necessary  to  that  re-dis- 
tribution of  Matter  and  Motion  which  constitutes  Evolution, 
are  fulfilled  in  a  far  higher  degree  than  at  first  appears. 

The  mutual  affinities  of  the  chief  organic  elements  are  not 
active  within  the  limits  of  those  temperatures  at  which 
organic  actions  take  place;  and  one  of  these  elements  is 
especially  characterized  by  its  chemical  indifference.  The 
compounds  formed  by  these  elements  in  ascending  grades  of 
complexity,  become  progressively  less  stable.  And  those 
most  complex  compounds  into  which  all  these  four  elements 
enter,  together  with  small  proportions  of  two  other  elements 


ORGANIC  MATTER.  25 

which  very  readily  oxidize,  have  an  instability  so  great  that 
decomposition  ensues  under  ordinary  atmospheric  conditions. 

Among  these  elements  out  of  which  living  bodies  are  built, 
there  is  an  unusual  tendency  to  unite  in  multiples;  and  so 
to  form  groups  of  products  which  have  the  same  chemical 
elements  in  the  same  proportions,  but,  differing  in  their 
modes  of  aggregation,  possess  different  properties.  This  pre- 
valence among  them  of  isomerism  and  polymerism,  shows,  in 
another  way,  the  special  fitness  of  organic  substances  for 
undergoing  re-distributions  of  their  components. 

In  those  most  complex  compounds  that  are  instrumental 
to  vital  actions,  there  exists  a  kind  and  degree  of  molecular 
mobility  which  constitutes  the  plastic  quality  fitting  them 
for  organization.  Instead  of  the  extreme  molecular  mobility 
possessed  by  three  out  of  the  four  organic  elements  in  their 
separate  states — instead  of  the  diminished,  but  still  great, 
molecular  mobility  possessed  by  their  simpler  combinations, 
the  gaseous  and  liquid  characters  of  which  unfit  them  for 
showing  to  any  extent  the  process  of  Evolution — instead  of 
the  physical  properties  of  their  less  simple  combinations, 
which,  when  not  made  unduly  mobile  by  heat,  assume  the 
unduly  rigid  form  of  crystals;  we  have  in  these  colloids,  of 
which  organisms  are  mainly  composed,  just  the  required 
compromise  between  fluidity  and  solidity.  They  cannot  be 
reduced  to  the  unduly  mobile  conditions  of  liquid  and  gas; 
and  yet  they  do  not  assume  the  unduly  fixed  condition  usually 
characterizing  solids.  The  absence  of  power  to  unite  together 
in  polar  arrangement,  leaves  their  molecules  with  a  certain 
freedom  of  relative  movement,  which  makes  them  sensitive 
to  small  forces,  and  produces  plasticity  in  the  aggregates 
composed  of  them. 

While  the  relatively  great  inertia  of  these  large  and  com- 
plex organic  molecules  renders  them  comparatively  incapable 
of  being  set  in  motion  by  the  ethereal  undulations,  and  so 
reduced  to  less  coherent  forms  of  aggregation,  this  same 
inertia  facilitates  changes  of  arrangement  among  their  con- 


24  THE  DATA  OP  BIOLOGY. 

molecules  are  more  heterogeneous  than  these  elements ;  tri- 
atomic  more  heterogeneous  than  diatomic ;  and  the  molecules 
containing  four  elements  more  heterogeneous  than  those  con- 
taining three:  the  most  heterogeneous  of  them  being  the 
proteids,  which  contain  two  other  elements.  The  hydrated 
forms  of  all  these  compounds  are  more  heterogeneous  than 
are  the  anhydrous  forms.  And  most  heterogeneous  of  all 
are  the  molecules  which,  besides  containing  three,  four,  or 
more  elements,  also  exhibit  the  isomerism  and  polymerism 
which  imply  unions  in  multiples. 

3.  This  formation  of  molecules  more  and  more  heteroge- 
neous during  terrestrial  evolution,  has  been  accompanied  by 
increasing  heterogeneity  in  the  aggregate  of  compounds  of 
each  kind,  as  well  as  an  increasing  number  of  kinds;  and 
this  increasing  heterogeneity  is  exemplified  in  an  extreme 
degree  in  the  compounds,  non-nitrogenous  and  nitrogenous, 
out  of  which  organisms  are  built.  So  that  the  classes, 
orders,  genera,  and  species  of  chemical  substances,  gradually 
increasing  as  the  Earth  has  assumed  its  present  form,  in- 
creased in  a  transcendent  degree  during  that  stage  which 
preceded  the  origin  of  life. 

§  9.  Returning  now  from  these  partially-parenthetic  ob- 
servations, and  summing  up  the  contents  of  the  preceding 
pages,  we  have  to  remark  that  in  the  substances  of  which  or- 
ganisms are  composed,  the  conditions  necessary  to  that  re-dis- 
tribution of  Matter  and  Motion  which  constitutes  Evolution, 
are  fulfilled  in  a  far  higher  degree  than  at  first  appears. 

The  mutual  affinities  of  the  chief  organic  elements  are  not 
active  within  the  limits  of  those  temperatures  at  which 
organic  actions  take  place;  and  one  of  these  elements  is 
especially  characterized  by  its  chemical  indifference.  The 
compounds  formed  by  these  elements  in  ascending  grades  of 
complexity,  become  progressively  less  stable.  And  those 
most  complex  compounds  into  which  all  these  four  elements 
enter,  together  with  small  proportions  of  two  other  elements 


ORGANIC  MATTER.  25 

which  very  readily  oxidize,  have  an  instability  so  great  that 
decomposition  ensues  under  ordinary  atmospheric  conditions. 

Among  these  elements  out  of  which  living  bodies  are  built, 
there  is  an  unusual  tendency  to  unite  in  multiples;  and  so 
to  form  groups  of  products  which  have  the  same  chemical 
elements  in  the  same  proportions,  but,  differing  in  their 
modes  of  aggregation,  possess  different  properties.  This  pre- 
valence among  them  of  isomerism  and  polymerism,  shows,  in 
another  way,  the  special  fitness  of  organic  substances  for 
undergoing  re-distributions  of  their  components. 

In  those  most  complex  compounds  that  are  instrumental 
to  vital  actions,  there  exists  a  kind  and  degree  of  molecular 
mobility  which  constitutes  the  plastic  quality  fitting  them 
for  organization.  Instead  of  the  extreme  molecular  mobility 
possessed  by  three  out  of  the  four  organic  elements  in  their 
separate  states — instead  of  the  diminished,  but  still  great, 
molecular  mobility  possessed  by  their  simpler  combinations, 
the  gaseous  and  liquid  characters  of  which  unfit  them  for 
showing  to  any  extent  the  process  of  Evolution — instead  of 
the  physical  properties  of  their  less  simple  combinations, 
which,  when  not  made  unduly  mobile  by  heat,  assume  the 
unduly  rigid  form  of  crystals;  we  have  in  these  colloids,  of 
which  organisms  are  mainly  composed,  just  the  required 
compromise  between  fluidity  and  solidity.  They  cannot  be 
reduced  to  the  unduly  mobile  conditions  of  liquid  and  gas; 
and  yet  they  do  not  assume  the  unduly  fixed  condition  usually 
characterizing  solids.  The  absence  of  power  to  unite  together 
in  polar  arrangement,  leaves  their  molecules  with  a  certain 
freedom  of  relative  movement,  which  makes  them  sensitive 
to  small  forces,  and  produces  plasticity  in  the  aggregates 
composed  of  them. 

While  the  relatively  great  inertia  of  these  large  and  com- 
plex organic  molecules  renders  them  comparatively  incapable 
of  being  set  in  motion  by  the  ethereal  undulations,  and  so 
reduced  to  less  coherent  forms  of  aggregation,  this  same 
inertia  facilitates  changes  of  arrangement  among  their  con- 


28  THE  DATA  OP  BIOLOGY. 

Colloids  take  up  by  a  power  called  "  capillary  affinity,"  a 
large  quantity  of  water:  undergoing  at  the  same  time  great 
increase  of  bulk  with  change  of  form.  Conversely,  with 
like  readiness,  they  give  up  this  water  by  evaporation; 
resuming,  partially  or  completely,  their  original  states. 
Whether  resulting  from  capillarity,  or  from  the  relatively 
great  diffusibility  of  water,  or  from  both,  these  changes  are 
to  be  here  noted  as  showing  another  mode  in  which  the 
arrangements  of  parts  in  organic  bodies  are  affected  by  me- 
chanical actions. 

In  what  is  termed  osmose,  we  have  a  further  mode  of  an 
allied  kind.  When  on  opposite  sides  of  a  permeable  septum, 
and  especially  a  septum  of  colloidal  substance,  are  placed 
miscible  solutions  of  different  densities,  a  double  transfer 
takes  place :  a  large  quantity  of  the  less  dense  solution  finds 
its  way  through  the  septum  into  the  more  dense  solution; 
and  a  small  quantity  of  the  more  dense  finds  its  way  into 
the  less  dense — one  result  being  a  considerable  increase  in 
the  bulk  of  the  more  dense  at  the  expense  of  the  less  dense. 
This  process,  which  appears  to  depend  on  several  conditions, 
is  not  yet  fully  understood.  But  be  the  explanation  what  it 
may,  the  process  is  one  that  tends  continually  to  work  altera- 
tions in  organic  bodies.  Through  the  surfaces  of  plants  and 
animals,  transfers  of  this  kind  are  ever  taking  place.  Many 
of  the  conspicuous  changes  of  form  undergone  by  organic 
germs,  are  due  mainly  to  the  permeation  of  their  limiting 
membranes  by  the  surrounding  liquids. 

It  should  be  added  that  besides  the  direct  alterations'which 
the  imbibition  and  transmission  of  water  and  watery  solutions 
by  colloids  produce  in  organic  matter,  they  produce  indirect 
alterations.  Being  instrumental  in  conveying  into  the  tissues 
the  agents  of  chemical  change,  and  conveying  out  of  them 
the  products  of  chemical  change,  they  aid  in  carrying  on 
other  re-distributions. 

§  12.  As  elsewhere  shown  (First  Principles,  §  100)  heat. 


THE  ACTIONS  OP  FORCES  ON  ORGANIC  MATTER.     29 

or  a  raised  state  of  molecular  vibration,  enables  incident  forces 
more  easily  to  produce  changes  of  molecular  arrangement  in 
organic  matter.  But  besides  this,  it  conduces  to  certain  vital 
changes  in  so  direct  a  way  as  to  become  their  chief  cause. 

The  power  of  the  organic  colloids  to  imbibe  water,  and  to 
bring  along  with  it  into  their  substance  the  materials  which 
work  transformations,  would  not  be  continuously  operative 
if  the  water  imbibed  were  to  remain.  It  is  because  it 
escapes,  and  is  replaced  by  more  water  containing  more 
materials,  that  the  succession  of  changes  is  maintained. 
Among  the  higher  animals  and  higher  plants  its  escape  is 
facilitated  by  evaporation.  And  the  rate  of  evaporation  is, 
other  things  equal,  determined  by  heat.  >  Though  the 

current  of  sap  in  a  tree  is  partly  dependent  on  some  action, 
probably  osmotic,  that  goes  on  in  the  roots;  yet  the  loss  of 
water  from  the  surfaces  of  the  leaves,  and  the  consequent 
absorption  of  more  sap  into  the  leaves  by  capillary  attraction, 
must  be  a  chief  cause  of  the  circulation.  The  drooping  of  a 
plant  when  exposed  to  the  sunshine  while  the  earth  round 
its  roots  is  dry,  shows  us  how  evaporation  empties  the  sap- 
vessels;  and  the  quickness  with  which  a  withered  slip  re- 
vives on  being  placed  in  water,  shows  us  the  part  which 
capillary  action  plays.  In  so  far,  then,  as  the  evaporation 
from  a  plant's  surface  helps  to  produce  currents  of  sap 
through  the  plant,  we  must  regard  the  heat  which  produces 
this  evaporation  as  a  part-cause  of  those  re-distributions  of 
matter  which  these  currents  effect.  In  terrestrial 

animals,  heat,  by  its  indirect  action  as  well  as  by  its  direct 
action,  similarly  aids  the  changes  that  are  going  on.  The 
exhalation  of  vapour  from  the  lungs  and  the  surface  of  the 
skin,  forming  the  chief  escape  of  the  water  that  is  swallowed, 
conduces  to  the  maintenance  of  those  currents  through  the 
tissues  without  which  the  functions  would  cease.  For 
though  the  vascular  system  distributes  nutritive  liquids  in 
ramified  channels  through  the  body;  yet  the  absorption  of 
these  liquids  into  tissues,  partly  depends  on  the  escape  of 


30  THE  DATA  OP  BIOLOGY. 

liquids  which  the  tissues  already  contain.  Hence,  to  the 
extent  that  such  escape  is  facilitated  by  evaporation,  and  this 
evaporation  facilitated  by  heat,  heat  becomes  an  agent  of  re- 
distribution in  the  animal  organism.* 

§  13.  Light,  which  is  now  known  to  modify  many  inor- 
ganic compounds — light,  which  works  those  chemical  changes 
utilized  in  photography,  causes  the  combinations  of  certain 
gases,  alters  the  molecular  arrangements  of  many  crystals, 
and  leaves  traces  of  its  action  even  on  substances  that  are 
extremely  stable, — may  be  expected  to  produce  marked  effects 
on  substances  so  complex  and  unstable  as  those  which  make 
up  organic  bodies.  It  does  produce  such  effects;  and  some 
of  them  are  among  the  most  important  that  organic  matter 
undergoes. 

The  molecular  changes  wrought  by  light  in  animals  are 
of  but  secondary  moment.  There  is  the  darkening  of  the 
skin  that  follows  exposure  to  the  Sun's  rays.  There  are 
those  alterations  in  the  retina  which  cause  in  us  sensations 
of  colours.  And  on  certain  eyeless  creatures  that  are  semi- 
transparent,  the  light  permeating  their  substance  works  some 
effects  evinced  by  movements.  But  speaking  generally, 
the  opacity  of  animals  limits  the  action  of  light  to  their 
surfaces;  and  so  renders  its  direct  physiological  influence 

*  The  remark  made  by  a  critic  to  the  effect  ihat  in  a  mammal  higher  tem- 
perature diminishes  the  rate  of  molecular  change  in  the  tissues,  leads  me  to 
add  that  the  exhalation  I  have  alleged  is  prevented  if  the  heat  rises  above  the 
range  of  variation  normal  to  the  organism ;  since,  then,  unusually  rapid  pulsa- 
tions with  consequent  inefficient  propulsion  of  the  blood,  cause  a  diminished 
rate  of  circulation.  To  produce  the  effect  referred  to  in  the  text,  heat  must 
be  associated  with  dryness ;  for  otherwise  evaporation  is  not  aided.  General 
evidence  supporting  the  statement  I  have  made  is  furnished  by  the  fact  that 
the  hot  and  dry  air  of  the  eastern  deserts  is  extremely  invigorating;  by  the 
fact  that  all  the  energetic  and  conquering  races  of  men  have  come  from  the 
hot  and  dry  regions  marked  on  the  maps  as  rainless ;  and  by  the  fact  that 
travellers  in  Africa  comment  on  the  contrast  between  the  inhabitants  of  the 
hot  and  dry  regions  (relatively  elevated)  and  those  of  the  hot  and  moist 
regions :  active  and  inert  respectively. 


THE  ACTIONS  OF  FORCES  ON  ORGANIC  MATTER.     31 

but  small.*  On  plants,  however,  the  solar  rays  that 

produce  in  us  the  impression  of  yellow,  are  the  immediate 
agents  of  those  molecular  changes  through  which  are  hourly 
accumulated  the  materials  for  further  growth.  Experiments 
have  shown  that  when  the  Sun  shines  on  living  leaves,  they 
begin  to  exhale  oxygen  and  to  accumulate  carbon  and  hydro- 
gen— results  which  are  traced  to  the  decomposition,  by  the 
solar  rays,  of  the  carbonic  acid  and  water  absorbed.  It  is  now 
an  accepted  conclusion  that,  by  the  help  of  certain  classes 
of  the  ethereal  undulations  penetrating  their  leaves,  plants 
are  enabled  to  separate  from  the  associated  oxygen  those  two 
elements  of  which  their  tissues  are  chiefly  built  up. 

This  transformation  of  ethereal  undulations  into  certain 
molecular  re-arrangements  of  an  unstable  kind,  on  the  over- 
throw of  which  the  stored-up  forces  are  liberated  in  new 
forms,  is  a  process  that  underlies  all  organic  phenomena.  It 
will  therefore  be  well  if  we  pause  a  moment  to  consider 
whether  any  proximate  interpretation  of  it  is  possible.  Ee- 
searches  in  molecular  physics  give  us  some  clue  to  its  nature. 

The  elements  of  the  problem  are  these : — The  atoms  f  of 
several  ponderable  matters  exist  in  combination :  those  which 
are  combined  having  strong  affinities,  but  having  also  affin- 
ities less  strong  for  some  of  the  surrounding  atoms  that  are 
otherwise  combined.  The  atoms  thus  united,  and  thus  mixed 
among  others  with  which  they  are  capable  of  uniting,  are 
exposed  to  the  undulations  of  a  medium  that  is  so  rare  as  to 
seem  imponderable.  These  undulations  are  of  numerous 
kinds :  they  differ  greatly  in  their  lengths,  or  in  the  fre- 

*  The  increase  of  respiration  found  to  result  from  the  presence  of  light,  is 
probably  an  indirect  effect.  It  is  most  likely  due  to  the  reception  of  more 
vivid  impressions  through  the  eyes,  and  to  the  consequent  nervous  stimulation. 
Bright  light  is  associated  in  our  experience  with  many  of  our  greatest  out- 
door pleasures,  and  its  presence  partially  arouses  the  consciousness  of  them, 
with  the  concomitant  raised  vital  functions. 

f  To  exclude  confusion  it  may  be  well  here  to  say  that  the  word  "  atom  " 
is,  as  before  explained,  used  as  the  name  for  a  unit  of  a  substance  at  present 
undecomposed ;  while  the  word  " molecule"  ie  used  as  the  name  for  a  unit  of 
a  substance  known  to  be  compound. 


32  THE  DATA  OF  BIOLOGY. 

quency  with  which  they  recur  at  any  given  point.  And 
under  the  influence  of  undulations  of  a  certain  frequency, 
some  of  these  atoms  are  transferred  from  atoms  for  which  they 
have  a  stronger  affinity,  to  atoms  for  which  they  have  a  weaker 
affinity.  That  is  to  say,  particular  orders  of  waves  of  a  rela- 
tively imponderable  matter,  remove  particular  atoms  of  pon- 
derable matter  from  their  attachments,  and  carry  them  within 
reach  of  other  attachments.  Now  the  discoveries  of 

Bunsen  and  Kirchoff  respecting  the  absorption  of  particular 
luminiferous  undulations  by  the  vapours  of  particular  sub- 
stances, joined  with  Prof.  Tyndall's  discoveries  respecting 
the  absorption  of  heat  by  gases,  show  very  clearly  that  the 
atoms  of  each  substance  have  a  rate  of  vibration  in  harmony 
with  ethereal  waves  of  a  certain  length,  or  rapidity  of  recur- 
rence. Every  special  kind  of  atom  can  be  made  to  oscillate 
by  a  special  order  of  ethereal  waves,  which  are  absorbed  in 
producing  its  oscillations ;  and  can  by  its  oscillations  generate 
this  same  order  of  ethereal  waves.  Whence  it  appears  that 
immense  as  is  the  difference  in  density  between  ether  and 
ponderable  matter,  the  waves  of  the  one  can  set  the  atoms  of 
the  other  in  motion,  when  the  successive  impacts  of  the  waves 
are  so  timed  as  to  correspond  with  the  oscillations  of  the 
atoms.  The  effects  of  the  waves  are,  in  such  case,  cumula- 
tive; and  each  atom  gradually  acquires  a  momentum  made 
up  of  countless  infinitesimal  momenta.  Note,  further, 

that  unless  the  members  of  a  chemically-compound  molecule 
are  so  bound  up  as  to  be  incapable  of  any  relative  movements 
(a  supposition  at  variance  with  the  conceptions  of  modern 
science)  we  must  conceive  them  as  severally  able  to  vibrate 
in  unison  or  harmony  with  those  same  classes  of  ethereal 
waves  that  affect  them  in  their  uncombined  states.  While 
the  compound  molecule  as  a  whole  will  have  some  new  rate 
of  oscillation  determined  by  its  attributes  as  a  whole;  its 
components  will  retain  their  original  rates  of  oscillation,  sub- 
ject only  to  modifications  by  mutual  influence.  Such 
being  the  circumstances  of  the  case  we  may  partially  under- 


THE  ACTIONS  OF  FORCES  OX  ORGANIC  MATTER.  33 

stand  how  the  Sun's  rays  can  effect  chemical  decompositions. 
If  the  members  of  a  diatomic  molecule  stand  so  related  to  the 
undulations  falling  on  them,  that  one  is  thrown  into  a  state  of 
increased  oscillation  and  the  other  not;  it  is  manifest  that 
there  must  arise  a  tendency  towards  the  dislocation  of  the 
two — a  tendency  which  may  or  may  not  take  effect,  accord- 
ing to  the  weakness  or  strength  of  their  union,  and  according 
to  the  presence  or  absence  of  collateral  affinities.  This  in- 
ference is  in  harmony  with  several  significant  facts.  Dr. 
Draper  remarks  that  "  among  metallic  substances  (com- 
pounds) those  first  detected  to  be  changed  by  light,  such  as  sil- 
ver, gold,  mercury,  lead,  have  all  high  atomic  weights;  and 
such  as  sodium  and  potassium,  the  atomic  weights  of  which 
are  low,  appeared  to  be  less  changeable."  As  here  interpreted, 
the  fact  specified  amounts  to  this;  that  the  compounds  most 
readily  decomposed  by  light,  are  those  in  which  there  is  a 
marked  contrast  between  the  atomic  weights  of  the  consti- 
tuents, and  probably  therefore  a  marked  contrast  between  the 
rapidities  of  their  vibrations.  The  circumstance,  too,  that 
different  chemical  compounds  are  decomposed  or  modified  in 
different  parts  of  the  spectrum,  implies  that  there  is  a  rela- 
tion between  special  orders  of  undulations  and  special  orders 
of  molecules — doubtless  a  correspondence  between  the  rates  of 
these  undulations  and  the  rates  of  oscillation  which  some  of 
the  components  of  such  molecules  will  assume.  Strong 

confirmation  of  this  view  may  be  drawn  from  the  decomposing 
actions  of  those  longer  ethereal  waves  which  we  perceive  as 
heat.  On  contemplating  the  whole  series  of  diatomic  com- 
pounds, we  see  that  the  elements  which  are  most  remote  in 
their  atomic  weights,  as  hydrogen  and  the  noble  metals  gen- 
erally, will  not  combine  at  all,  or  do  so  with  great  diffi- 
culty: their  vibrations  are  so  unlike  that  they  cannot  keep 
together  under  any  conditions  of  temperature.  If,  again, 
we  look  at  a  smaller  group,  as  the  metallic  oxides,  we  see  that 
whereas  those  metals  which  have  atoms  nearest  in  weight  to 
the  atoms  of  oxygen,  cannot  be  separated  from  oxygen  by 


34  THE  DATA  OP  BIOLOGY. 

heat,  even  when  it  is  joined  by  a  powerful  collateral  affinity; 
those  metals  which  differ  more  widely  from  oxygen  in  their 
atomic  weights,  can  be  de-oxidized  by  carbon  at  high  tem- 
peratures; and  those  which  differ  from  it  most  widely  com- 
bine with  it  very  reluctantly,  and  yield  it  up  if  exposed  to 
thermal  undulations  of  moderate  intensity.  Here  indeed, 
remembering  the  relations  among  the  atomic  weights  in  the 
two  cases,  may  we  not  suspect  a  close  analogy  between  the 
de-oxidation  of  a  metallic  oxide  by  carbon  under  the  influence 
of  the  longer  ethereal  waves,  and  the  de-carbonization  of 
carbonic  acid  by  hydrogen  under  the  influence  of  the  shorter 
ethereal  waves? 

These  conceptions  help  us  to  some  dim  notion  of  the  mode 
in  which  changes  are  wrought  in  light  in  the  leaves  of  plants. 
Among  the  several  elements  concerned,  there  are  wide  differ- 
ences in  molecular  mobility,  and  probably  in  the  rates  of 
molecular  vibration.  Each  is  combined  with  one  of  the  others, 
but  is  capable  of  forming  various  combinations  with  the  rest. 
And  they  are  severally  in  presence  of  a  complex  compound 
into  which  they  all  enter,  and  which  is  ready  to  assimilate 
with  itself  the  new  compound  molecules  they  form.  Certain 
of  the  ethereal  waves  falling  on  them  when  thus  arranged, 
cause  a  detachment  of  some  of  the  combined  atoms  and  a 
union  of  the  rest.  And  the  conclusion  suggested  is  that 
the  induced  vibrations  among  the  various  atoms  as  at  first 
arranged,  are  so  incongruous  as  to  produce  instability,  and 
to  give  collateral  affinities  the  power  to  work  a  rearrange- 
ment which,  though  less  stable  under  other  conditions, 
is  more  stable  in  the  presence  of  these  particular  undula- 
tions. There  seems,  indeed,  no  choice  but  to  conceive 
the  matter  thus.  An  atom  united  with  one  for  which  it  has 
a  strong  affinity,  has  to  be  transferred  to  another  for  which 
it  has  a  weaker  affinity.  This  transfer  implies  motion.  The 
motion  is  given  by  the  waves  of  a  medium  that  is  relatively 
imponderable.  No  one  wave  of  this  imponderable  medium 
can  give  the  requisite  motion  to  this  atom  of  ponderable 


THE  ACTIONS  OP  FORCES  ON  ORGANIC  MATTER.     35 

matter :  especially  as  the  atom  is  held  by  a  positive  force  be- 
sides its  inertia.  The  motion  required  can  hence  be  given  only 
by  successive  waves;  and  that  these  may  not  destroy  each 
other's  effects,  it  is  needful  that  each  shall  strike  the  atom 
just  when  it  has  completed  the  recoil  produced  by  the  impact 
of  previous  ones.  That  is,  the  ethereal  undulations  must 
coincide  in  rate  with  the  oscillations  of  the  atom,  determined 
by  its  inertia  and  the  forces  acting  on  it.  It  is  also  requisite 
that  the  rate  of  oscillation  of  the  atom  to  be  detached,  shall 
differ  from  that  of  the  atom  with  which  it  is  united;  since 
if  the  two  oscillated  in  unison  the  ethereal  waves  would  not 
tend  to  separate  them.  And,  finally,  the  successive  impacts 
of  the  ethereal  waves  must  be  accumulated  until  the  resulting 
oscillations  have  become  so  wide  in  their  sweep  as  greatly  to 
weaken  the  cohesion  of  the  united  atoms,  at  the  same  time 
that  they  bring  one  of  them  within  reach  of  other  atoms  with 
which  it  will  combine.  In  this  way  only  does  it  seem  possible 
for  such  a  force  to  produce  such  a  transfer.  More- 

over, while  we  are  thus  enabled  to  conceive  how  light  may 
work  these  molecular  changes,  we  also  gain  an  insight  into 
the  method  by  which  the  insensible  motions  propagated  to 
us  from  the  Sun,  are  treasured  up  in  such  ways  as  afterwards 
to  generate  sensible  motions.  By  the  accumulation  of  in- 
finitesimal impacts,  atoms  of  ponderable  matter  are  made  to 
oscillate.  The  quantity  of  motion  which  each  of  them  even- 
tually acquires,  effects  its  transfer  to  a  position  of  unstable 
equilibrium,  from  which  it  can  afterwards  be  readily  dis- 
lodged. And  when  so  dislodged,  along  with  other  atoms 
similarly  and  simultaneously  affected,  there  is  suddenly  given 
out  all  the  motion  which  had  been  before  impressed  on  it. 

Speculation  aside,  however,  that  which  it  concerns  us  to 
notice  is  the  broad  fact  that  light  is  an  all-important  agent 
of  molecular  changes  in  organic  substances.  It  is  not  here 
necessary  for  us  to  ascertain  how  light  produces  these  com- 
positions and  decompositions.  It  is  necessary  only  for  us  to 
observe  that  it  does  produce  them.  That  the  characteristic 


36  THE  DATA  OP  BIOLOGY. 

matter  called  chlorophyll,  which  gives  the  green  colour  to 
leaves,  makes  its  appearance  whenever  the  blanched  shoots 
of  plants  are  exposed  to  the  Sun ;  that  the  petals  of  flowers, 
uncoloured  while  in  the  bud,  acquire  their  bright  tints  as 
they  unfold;  and  that  on  the  outer  surfaces  of  animals, 
analogous  changes  are  induced;  are  wide  inductions  which 
are  enough  for  our  present  purpose. 

§  14.  We  come  next  to  the  agency  of  chief  importance 
among  those  that  work  changes  in  organic  matter;  namely, 
chemical  affinity.  How  readily  vegetal  and  animal  substances 
are  modified  by  other  substances  put  in  contact  with  them, 
we  see  daily  illustrated.  Besides  the  many  compounds  which 
cause  the  death  of  an  organism  into  which  they  are  put,  we 
have  the  much  greater  number  of  compounds  which  work 
those  milder  effects  termed  medicinal — effects  implying,  like 
the  others,  molecular  re-arrangements.  Indeed,  most  soluble 
chemical  compounds,  natural  and  artificial,  produce,  when 
taken  into  the  body,  alterations  that  are  more  or  less  mani- 
fest in  their  results. 

After  what  was  shown  in  the  last  chapter,  it  will  be  mani- 
fest that  this  extreme  modifiability  of  organic  matter  by 
chemical  agencies,  is  the  chief  cause  of  that  active  molecular 
re-arrangement  which  organisms,  and  especially  animal 
organisms,  display.  In  the  two  fundamental  functions  of 
nutrition  and  respiration,  we  have  the  means  by  which  the 
supply  of  materials  for  this  active  molecular  re-arrangement 
is  maintained. 

The  process  of  animal  nutrition  consists  partly  in  the  ab- 
sorption of  those  complex  substances  which  are  thus  highly 
capable  of  being  chemically  altered,  and  partly  in  the  absorp- 
tion of  simpler  substances  capable  of  chemically  altering  them. 
The  tissues  always  contain  small  quantities  of  alkaline  and 
earthy  salts,  which  enter  the  system  in  one  form  and  are 
excreted  in  another.  Though  we  do  not  know  specifically 
the  parts  which  these  salts  play,  yet  from  their  universal 


THE  ACTIONS  OF  FORCES  ON  ORGANIC  MATTER.     37 

presence,  and  from  the  transformations  which  they  undergo 
in  the  body,  it  may  be  safely  inferred  that  their  chemical 
affinities  are  instrumental  in  working  some  of  the  meta- 
morphoses ever  going  on. 

The  inorganic  substance,  however,  on  which  mainly  depend 
these  metamorphoses  in  organic  matter,  is  not  swallowed 
along  with  the  solid  and  liquid  food,  but  is  absorbed  from 
the  surrounding  medium — air  or  water,  as  the  case  may  be. 
Whether  the  ox}-gen  taken  in,  either,  as  by  the  lowest  ani- 
mals, through  the  general  surface,  or,  as  by  the  higher  ani- 
mals, through  respiratory  organs,  is  the  immediate  cause 
of  those  molecular  changes  which  are  ever  going  on  through- 
out the  living  tissues;  or  whether  the  oxygen,  playing  the 
part  of  scavenger,  merely  aids  these  changes  by  carrying 
away  the  products  of  decompositions  otherwise  caused;  it 
equally  remains  true  that  these  changes  are  maintained  by 
its  instrumentality.  Whether  the  oxygen  absorbed  and  dif- 
fused through  the  system  effects  a  direct  oxidation  of  the 
organic  colloids  which  it  permeates,  or  whether  it  first  leads 
to  the  formation  of  simpler  and  more  oxidized  compounds, 
which  are  afterwards  further  oxidized  and  reduced  to  still 
simpler  forms,  matters  not,  in  so  far  as  the  general  result  is 
concerned.  In  any  case  it  holds  good  that  the  substances  of 
which  the  animal  body  is  built  up,  enter  it  in  either  an  un- 
oxidized  or  in  a  but  slightly  oxidized  and  highly  unstable 
state;  while  the  great  mass  of  them  leave  it  in  a  fully 
oxidized  and  stable  state.  It  follows,  therefore,  that,  what- 
ever the  special  changes  gone*  through,  the  general  process  is 
a  falling  from  a  state  of  unstable  chemical  equilibrium  to  a 
state  of  stable  chemical  equilibrium.  Whether  this  process 
be  direct  or  indirect,  the  total  molecular  re-arrangement  and 
the  total  motion  given  out  in  effecting  it,  must  be  the  same. 

§  15.  There  is  another  species  of  re-distribution  among 
the  component  matters  of  organisms,  which  is  not  immediately 
effected  by  the  affinities  of  the  matters  concerned,  but  is  me- 
4 


38  THE  DATA  OP  BIOLOGY. 

diately  effected  by  other  affinities;  and  there  is  reason  to 
think  that  the  re-distribution  thus  caused  is  important  in 
amount,  if  not  indeed  the  most  important.  In  ordinary  cases 
of  chemical  action,  the  two  or  more  substances  concerned 
themselves  undergo  changes  of  molecular  arrangement;  and 
the  changes  are  confined  to  the  substances  themselves.  But 
there  are  other  cases  in  which  the  chemical  action  going  on 
does  not  end  with  the  substances  at  first  concerned,  but  sets 
up  chemical  actions,  or  changes  of  molecular  arrangement, 
among  surrounding  substances  that  would  else  have  remained 
quiescent.  And  there  are  yet  further  cases  in  which  mere 
contact  with  a  substance  that  is  itself  quiescent,  will  cause 
other  substances  to  undergo  rapid  metamorphoses.  In 

what  we  call  fermentation,  the  first  species  of  this  communi- 
cated chemical  action  is  exemplified.  One  part  of  yeast,  while 
itself  undergoing  molecular  change,  will  convert  100  parts  of 
sugar  into  alcohol  and  carbonic  acid;  and  during  its  own 
decomposition,  one  part  of  diastase  "  is  able  to  effect  the 
transformation  of  more  than  1000  times  its  weight  of  starch 
into  sugar."  As  illustrations  of  the  second  species,  may 
be  mentioned  those  changes  which  are  suddenly  produced 
in  many  colloids  by  minute  portions  of  various  substances 
added  to  them — subtances  that  are  not  undergoing  manifest 
transformations,  and  suffer  no  appreciable  effects  from  the 
contact.  The  nature  of  the  first  of  these  two  kinds  of 

communicated  molecular  change,  which  here  chiefly  concerns 
us,  may  be  rudely  represented  by  certain  visible  changes 
communicated  from  mass  to  mass,  when  a  series  of  masses 
has  been  arranged  in  a  special  way.  The  simplest  example  is 
that  furnished  by  the  child's  play  of  setting  bricks  on  end 
in  a  row,  in  such  positions  that  when  the  first  is  overthrown 
it  overthrows  the  second,  the  second  the  third,  the  third  the 
fourth,  and  so  on  to  the  end  of  the  row.  Here  we  have  a 
number  of  units  severally  placed  in  unstable  equilibrium, 
and  in  such  relative  positions  that  each,  while  falling  into  a 
state  of  stable  equilibrium,  gives  an  impulse  to  the  next 


THE  ACTIONS  OP  FORCES  ON  ORGANIC  MATTER.     39 

sufficient  to  make  the  next,  also,  fall  from  unstable  to  stable 
equilibrium.  Now  since,  among  mingled  compound  mole- 
cules, no  one  can  undergo  change  in  the  arrangement  of  its 
parts  without  a  molecular  motion  that  must  cause  some  dis- 
turbance all  round;  and  since  an  adjacent  molecule  dis- 
turbed by  this  communicated  motion,  may  have  the  arrange- 
ment of  its  constituent  atoms  altered,  if  it  is  not  a  stable 
arrangement;  and  since  we  know,  both  that  the  molecules 
which  are  changed  by  this  so-called  catalysis  are  unstable,  and 
that  the  molecules  resulting  from  their  changes  are  more 
stable;  it  seems  probable  that  the  transformation  is  really 
analogous,  in  principle,  to  the  familiar  one  named.  Whether 
thus  interpretable  or  not,  however,  there  is  good  reason  for 
thinking  that  to  this  kind  of  action  is  due  a  large  amount  of 
vital  metamorphosis.  Let  us  contemplate  the  several  groups 
of  facts  which  point  to  this  conclusion.*' 

In  the  last  chapter  (§2)  we  incidentally  noted  the  extreme 
instability  of  nitrogenous  compounds  in  general.  We  saw 
that  sundry  of  them  are  liable  to  explode  on  the  slightest 
incentive — sometimes  without  any  apparent  cause;  and  that 
of  the  rest,  the  great  majority  are  very  easily  decomposed  by 
heat,  and  by  various  substances.  We  shall  perceive  much 
significance  in  this  general  characteristic  when  we  join  it 
with  the  fact  that  the  substances  capable  of  setting  up  exten- 
sive molecular  changes  in  the  way  above  described  are  all 
nitrogenous  ones.  Yeast  consists  of  vegetal  cells  containing 

*  On  now  returning  to  the  subject  after  many  years,  I  meet  with  some 
evidence  recently  assigned,  in  a  paper  read  before  the  Royal  Society  by  Mr.  J. 
W.  Pickering,  D.Sc.  (detailing  results  harmonizing  with  those  obtained  by 
Prof.  Grimaux),  showing  clearly  how  important  an  agent  in  vital  actions  is 
this  production  of  isomeric  changes  by  slight  changes  of  conditions.  Certain 
artificially  produced  substances,  simulating  proteids  in  other  of  their  charac- 
ters and  reactions,  were  found  to  simulate  them  in  coagulability  by  trifling 
disturbances.  "  In  the  presence  of  a  trace  of  neutral  salt  they  coagulate  on 
heating  at  temperatures  very  similar  to  proteid  solutions."  And  it  is  shown 
that  by  one  of  these  factitious  organic  colloids  a  like  effect  is  produced  in 
coagulating  the  blood,  to  that  "  produced  by  the  intravenous  injection  of  a 
nucleoproteid." 


40  THE  DATA  OP  BIOLOGY. 

nitrogen, — cells  that  grow  by  assimilating  the  nitrogenous 
matter  contained  in  wort.  Similarly,  the  "  vinegar-plant," 
which  greatly  facilitates  the  formation  of  acetic  acid  from 
alcohol,  is  a  fungoid  growth  that  is  doubtless,  like  others  of 
its  class,  rich  in  nitrogenous  compounds.  Diastase,  by  which 
the  transformation  of  starch  into  sugar  is  effected  during 
the  process  of  malting,  is  also  a  nitrogenous  body.  So  too  is 
a  substance  called  synaptase — an  albumenous  principle  con- 
tained in  almonds,  which  has  the  power  of  working  several 
metamorphoses  in  the  matters  associated  with  it.  These 
nitrogenized  compounds,  like  the  rest  of  their  family,  are 
remarkable  for  the  rapidity  with  which  they  decompose ;  and 
the  extensive  changes  produced  by  them  in  the  accompanying 
carbo-hydrates,  are  found  to  vary  in  their  kinds  accord- 
ing as  the  decompositions  of  the  ferments  vary  in  their 
stages.  We  have  next  to  note,  as  having  here  a 

meaning  for  us,  the  chemical  contrasts  between  those  organ- 
isms which'  carry  on  their  functions  by  the  help  of  external 
forces,  and  those  which  carry  on  their  functions  by  forces 
evolved  from  within.  If  we  compare  animals  and  plants,  we 
see  that  whereas  plants,  characterized  as  a  class  by  containing 
but  little  nitrogen,  are  dependent  on  the  solar  rays  for  their 
vital  activities;  animals,  the  vital  activities  of  which  are  not 
thus  dependent,  mainly  consist  of  nitrogenous  substances. 
There  is  one  marked  exception  to  this  broad  distinction,  how- 
ever; and  this  exception  is  specially  instructive.  Among 
plants  there  is  a  considerable  group — the  Fungi — many  mem- 
bers of  which,  if  not  all,  can  live  and  grow  in  the  dark;  and 
it  is  their  peculiarity  that  they  are  .very  much  more  nitro- 
genous than  other  plants.  Yet  a  third  class  of  facts 
of  like  significance  is  disclosed  when  we  compare  different 
portions  of  the  same  organism.  The  seed  of  a  plant  contains 
nitrogenous  substance  in  a  far  higher  ratio  than  the  rest  of 
the  plant ;  and  the  seed  differs  from  the  rest  of  the  plant  in 
its  ability  to  initiate,  in  the  absence  of  light,  extensive  vital 
changes — the  changes  constituting  germination.  Similarly 


THE  ACTIONS  OF  FORCES  ON  ORGANIC  MATTER,     41 

in  the  bodies  of  animals,  those  parts  which  carry  on  active 
functions  are  nitrogenous;  while  parts  that  are  non-nitro- 
genous— as  the  deposits  of  fat— carry  on  no  active  functions. 
And  we  even  find  that  the  appearance  of  non-nitrogenous 
matter  throughout  tissues  normally  composed  almost  wholly 
of  nitrogenous  matter,  is  accompanied  by  loss  of  activity: 
what  is  called  fatty  degeneration  being  the  concomitant  of 
failing  vitality.  One  more  fact,  which  serves  to  make 

still  clearer  the  meaning  of  the  foregoing  ones,  remains — the 
fact,  namely,  that  in  no  part  of  any  organism  where  vital 
changes  are  going  on,  is  nitrogenous  matter  wholly  absent. 
It  is  common  to  speak  of  plants — or  at  least  all  parts  of 
plants  but  the  seeds — as  non-nitrogenous.  But  they  are  only 
relatively  so;  not  absolutely.  The  quantity  of  albumenoid 
substance  in  the  tissues  of  plants,  is  extremely  small  com- 
pared with  the  quantity  contained  in  the  tissues  of  animals; 
but  all  plant-tissues  which  are  discharging  active  functions 
have  some  albumenoid  substance.  In  every  living  vegetal 
cell  there  is  a  certain  part  that  includes  nitrogen  as  a  com- 
ponent. This  part  initiates  those  changes  which  constitute 
the  development  of  the  cell.  And  if  it  cannot  be  said  that  it 
is  the  worker  of  all  subsequent  changes  undergone  by  the 
cell,  it  nevertheless  continues  to  be  the  part  in  which  the 
independent  activity  is  most  marked. 

Looking  at  the  evidence  thus  brought  together,  do  we  not 
get  an  insight  into  the  actions  of  nitrogenous  matter  as  a 
worker  of  organic  changes?  We  see  that  nitrogenous  com- 
pounds in  general  are  extremely  prone  to  decompose:  their 
decomposition  often  involving  a  sudden  and  great  evolution 
of  energy.  We  see  that  the  substances  classed  as  ferments, 
which,  during  their  own  molecular  changes,  set  up  molecular 
changes  in  the  accompanying  carbo-hydrates,  are  all  nitro- 
genous. We  see  that  among  classes  of  organisms,  and  among 
the  parts  of  each  organism,  there  is  a  relation  between  the 
amount  of  nitrogenous  matter  present  and  the  amount  of 
independent  activity.  And  we  see  that  even  in  organisms 


42  THE  DATA  OF  BIOLOGY. 

and  parts  of  organisms  where  the  activity  is  least,  such 
changes  as  do  take  place  are  initiated  by  a  substance  contain- 
ing nitrogen.  Does  it  not  seem  probable,  then,  that  these 
extremely  unstable  compounds  have  everywhere  the  effect  of 
communicating  to  the  less  unstable  compounds  associated 
with  them,  molecular  movements  towards  a  stable  state,  like 
those  they  are  themselves  undergoing?  The  changes  which 
we  thus  suppose  nitrogenous  matter  to  produce  in  the  body, 
are  clearly  analogous  to  those  which  we  see  it  produce  out  of 
the  body.  Out  of  the  body,  certain  carbo-hydrates  in  con- 
tinued contact  with  nitrogenous  matter,  are  transformed  into 
carbonic  acid  and  alcohol,  and  unless  prevented  the  alcohol 
is  transformed  into  acetic  acid:  the  substances  formed 
being  thus  more  highly  oxidized  and  more  stable  than  the 
substances  destroyed.  In  the  body,  these  same  carbo- 
hydrates, in  continued  contact  with  nitrogenous  matter,  are 
transformed  into  carbonic  acid  and  water:  substances  which 
are  also  more  highly  oxidized  and  more  stable  than  those 
from  which  they  result.  And  since  acetic  acid  is  itself  re- 
solved by  further  oxidation  into  carbonic  acid  and  water; 
we  see  that  the  chief  difference  between  the  two  cases  is, 
that  the  process  is  more  completely  effected  in  the  body  than 
it  is  out  of  the  body.  Thus,  to  carry  further  the  simile  used 
above,  the  molecules  of  carbo-hydrates  contained  in  the  tis- 
sues are,  like  bricks  on  end,  not  in  the  stablest  equilibrium ; 
but  still  in  an  equilibrium  so  stable,  that  they  cannot  be 
overthrown  by  the  chemical  and  thermal  forces  which  the 
body  brings  to  bear  on  them.  On  the  other  hand,  being  like 
similarly-placed  bricks  that  have  very  narrow  ends,  the  nitro- 
genous molecules  contained  in  the  tissues  are  in  so  unstaWe 
an  equilibrium  that  they  cannot  withstand  these  forces. 
And  when  these  delicately-poised  nitrogenous  molecules 
fall  into  stable  arrangements,  they  give  impulses  to  the 
more  firmly-poised  non-nitrogenous  molecules,  which  cause 
them  also  to  fall  into  stable  arrangements.  It  is  a 

curious  and  significant  fact  that  in  the  arts,  we  not  only 


THE  ACTIONS  OF  FORCES  ON  ORGANIC   MATTER.     43 

utilize  this  same  principle  of  initiating  extensive  changes 
among  comparatively  stable  compounds,  by  the  help  of  com- 
pounds much  less  stable,  but  we  employ  for  the  purpose 
compounds  of  the  same  general  class.  Our  modern  method 
of  firing  a  gun  is  to  place  in  close  proximity  with  the  gun- 
powder which  we  wish  to  decompose  or  explode,  a  small  por- 
tion of  fulminating  powder,  which  is  decomposed  or  exploded 
with  extreme  facility,  and  which,  on  decomposing,  communi- 
cates the  consequent  molecular  disturbance  to  the  less-easily 
decomposed  gunpowder.  When  we  ask  what  this  fulminating 
powder  is  composed  of,  we  find  that  it  is  a  nitrogenous  salt.* 

Thus,  besides  the  molecular  re-arrangements  produced  in 
organic  matter  by  direct  chemical  action,  there  are  others  of 
kindred  importance  produced  by  indirect  chemical  action. 
Indeed,  the  inference  that  some  of  the  leading  transforma- 
tions occurring  in  the  animal  organism,  are  due  to  this 
so-called  catalysis,  appears  necessitated  by  the  general  aspect 
of  the  facts,  apart  from  any  such  detailed  interpretations  as 
the  foregoing.  We  know  that  various  amylaceous  and 
saccharine  matters  taken  as  food  do  not  appear  in  the 
excreta,  and  must  therefore  be  decomposed .  in  their  course 
through  the  body.  We  know  that  these  matters  do  not 
become  components  of  the  tissues,  but  only  of  the  con- 
tained liquids  and  solids ;  and  that  thus  their  metamorphosis 
is  not  a  direct  result  of  tissue-change.  We  know  that  their 
stability  is  such  that  the  thermal  and  chemical  forces  to 
which  they  are  exposed  in  the  body,  cannot  alone  decom- 
pose them.  The  only  explanation  open  to  us,  therefore,  is 
that  the  transformation  of  these  carbo-hydrates  into  carbonic 
acid  and  water,  is  due  to  communicated  chemical  action. 

*  After  this  long  interval  during  which  other  subjects  have  occupied  me, 
I  now  find  that  the  current  view  is  similar  to  the  view  above  set  forth,  in  so 
far  that  a  small  molecular  disturbance  is  supposed  suddenly  to  initiate  a  great 
one,  producing  a  change  compared  to  an  explosion.  But  while,  of  two  pro- 
posed interpretations,  one  is  that  the  fuse  is  nitrogenous  and  the  charge  a 
carbo-hydrate,  the  other  is  that  both  are  nitrogenous.  The  relative  probabili- 
ties of  these  alternative  views  will  be  considered  in  a  subsequent  chapter. 


44  THE   DATA  OP  BIOLOGY. 

§  16.  This  chapter  will  have  served  its  purpose  if  it  has 
given  a  conception  of  the  extreme  modifiability  of  organic 
matter  by  surrounding  agencies.  Even  were  it  possible, 
it  would  be  needless  to  describe  in  detail  the  immensely 
varied  and  complicated  changes  which  the  forces  from  mo- 
ment to  moment  acting  on  them,  work  in  living  bodies. 
Dealing  with  biology  in  its  general  principles,  it  concerns  us 
only  to  notice  how  specially  sensitive  are  the  substances  of 
which  organisms  are  built  up  to  the  varied  influences  that 
act  upon  organisms.  Their  special  sensitiveness  has  been 
made  sufficiently  manifest  in  the  several  foregoing  sections. 


CHAPTER  III. 

THE    RE-ACTIONS    OF    ORGANIC    MATTER    ON    FORCES. 

§  17.  EE-DISTRIBUTIONS  of  Matter  imply  concomitant  re- 
distributions of  Motion.  That  which  under  one  of  its  aspects 
we  contemplate  as  an  alteration  of  arrangement  among  the 
parts  of  a  body,  is,  under  a  correlative  aspect,  an  alteration 
of  arrangement  among  certain  momenta,  whereby  these  parts 
are  impelled  to  their  new  positions.  At  the  same  time  that 
a  force,  acting  differently  on  the  different  units  of  an  aggre- 
gate, changes  their  relations  to  one  another;  these  units,  re- 
acting differently  on  the  different  parts  of  the  force,  work 
equivalent  changes  in  the  relations  of  these  to  one  another. 
Inseparably  connected  as  they  are,  these  two  orders  of  phe- 
nomena are  liable  to  be  confounded  together.  It  is  very 
needful,  however,  to  distinguish  between  them.  In  the  last 
chapter  we  took  a  rapid  survey  of  the  re-distributions  which 
forces  produce  in  organic  matter;  and  here  we  must  take  a 
like  survey  of  the  simultaneous  re-distributions  undergone  by 
the  forces. 

At  the  outset  we  are  met  by  a  difficulty.  The  parts  of  an 
inorganic  mass  undergoing  re-arrangement  by  an  incident 
force,  are  in  most  cases  passive — do  not  complicate  those 
necessary  re-actions  that  result  from  their  inertia,  by  other 
forces  which  they  themselves  originate.  But  in  organic 
matter  the  re-arranged  parts  do  not  re-act  in  virtue  of  their 
inertia  only.  They  are  so  constituted  that  an  incident  force 
usually  sets  up  in  them  other  actions  which  are  much 
more  important.  Indeed,  what  we  may  call  the  indirect  re- 

45 


46  THE  DATA  OP  BIOLOGY. 

actions  thus  caused,  arc  so  great  in  their  amounts  compared 
with  the  direct  re-actions,  that  they  quite  obscure  them. 

The  impossibility  of  separating  these  two  kinds  of  re- 
action compels  us  to  disregard  the  distinction  between  them. 
Under  the  above  general  title,  we  must  include  both  the  im- 
mediate re-actions  and  those  re-actions  mediately  produced, 
which  are  among  the  most  conspicuous  of  vital  phenomena. 

§  18.  From  organic  matter,  as  from  all  other  matter,  in- 
cident forces  call  forth  that  re-action  which  we  know  as 
heat.  More  or  less  of  molecular  vibration  necessarily  results 
when,  to  the  forces  at  work  among  the  molecules  of  any 
aggregate,  other  forces  are  added.  Experiment  abundantly 
demonstrates  this  in  the  case  of  inorganic  masses;  and  it 
must  equally  hold  in  the  case  of  organic  masses.  In 

both  cases  the  force  which,  more  markedly  than  any  other, 
produces  this  thermal  re-action,  is  that  which  ends  in  the 
union  of  different  substances.  Though  inanimate  bodies  ad- 
mit of  being  greatly  heated  by  pressure  and  by  the  electric 
current,  yet  the  evolutions  of  heat,  thus  induced  are  neither 
so  common,  nor  in  most  cases  so  conspicuous,  as  those  result- 
ing from  chemical  combination.  And  though  in  animate 
bodies  there  are  certain  -amounts  of  heat  generated  by  other 
actions,  yet  these  are  secondary  to  the  heat  generated  by  the 
action  of  oxygen  on  the  substances  composing  the  tissues  and 
the  substances  contained  in  them.  Here,  however, 

we  see  one  of  the  characteristic  distinctions  between  inani- 
mate and  animate  bodies.  Among  the  first  there  are  but 
few  which  ordinarily  exist  in  a  condition  to  evolve  the  heat 
caused  by  chemical  combination;  and  such  as  are  in  this 
condition  soon  cease  to  be  so  when  chemical  combination 
and  genesis  of  heat  once  begin  in  them.  Whereas,  among 
the  second  there  universally  exists  the  ability,  more  or  less 
decided,  thus  to  evolve  heat;  and  the  evolution  of  heat,  in 
some  cases  very  slight  and  in  no  cases  very -great,  continues 
as  long  as  they  remain  animate  bodies. 


THE  RE-ACTIONS  OF  ORGANIC  MATTER  ON  FORCES.      47 

The  relation  between  active  change  of  matter  and  re-active 
genesis  of  molecular  vibration,  is  clearly  shown  by  the  con- 
trasts between  different  organisms,  and  between  different 
states  and  parts  of  the  same  organism.  In  plants  the  genesis, 
of  heat  is  extremely  small,  in  correspondence  with  their  ex- 
tremely small  production  of  carbonic  acid:  those  portions 
only,  as  flowers  and  germinating  seeds,  in  which  considerable 
oxidation  is  going  on,  having  decidedly  raised  temperatures. 
Among  animals  we  see  that  the  hot-blooded  are  those  which 
expend  much  force  and  respire  actively.  Though  insects  are 
scarcely  at  all  warmer  than  the  surrounding  air  when  they 
are  still,  they  rise  several  degrees  above  it  when  they  exert 
themselves;  and  in  mammals,  which  habitually  maintain  a 
temperature  much  higher  than  that  of  their  medium,  exertion 
is  accompanied  by  an  additional  production  of  heat. 

This  molecular  agitation  accompanies  the  falls  from  un- 
stable to  stable  molecular  combinations;  whether  they  be 
those  from  the  most  complex  to  the  less  complex  compounds, 
or  whether  they  be  those  ultimate  falls  which  end  in  fully 
oxidized  and  relatively  simple  compounds;  and  whether  they 
be  those  of  the  nitrogenous  matters  composing  the  tissues  or 
those  of  the  non-nitrogenous  matters  diffused  through  them. 
In  the  one  case  as  in  the  other,  the  heat  must  be  regarded  as 
a  concomitant.  Whether  the  distinction,  originally 

made  by  Liebig,  between  nitrogenous  substances  as  tissue- 
food  and  non-nitrogenous  substances  as  heat-food,  be  true  or 
not  in  a  narrower  sense,  it  cannot  be  accepted  in  the  sense 
that  tissue-food  is  not  also  heat-food.  Indeed  he  does  not 
himself  assert  it  in  this  sense.  The  ability  of  carnivorous 
animals  to  live  and  generate  heat  while  consuming  matter 
that  is  almost  exclusively  nitrogenous,  suffices  to  prove  that 
the  nitrogenous  compounds  forming  the  tissues  are  heat-pro- 
ducers, as  well  as  the  non-nitrogenous  compounds  circulating 
among  and  through  the  tissues :  a  conclusion  which  is  in- 
deed justified  by  the  fact  that  nitrogenous  substances  out  of 
the  body  yield  heat,  though  not  a  large  amount,  during 


48  THE  DATA  OP  BIOLOGY. 

combustion.  But  most  likely  this  antithesis  is  not 

true  even  in  the  more  restricted  sense.  The  probability  is 
that  the  hydrocarbons  and  carbo-hydrates  which,  in  travers- 
ing the  system,  are  transformed  by  communicated  chemical 
action,  evolve,  during  their  transformation,  not  heat  alone 
but  also  other  kinds  of  force.  It  may  be  that  as  the  nitro- 
genous matter,  while  falling  into  more  stable  molecular 
arrangements,  generates  both  that  molecular  agitation  called 
heat  and  such  other  molecular  movements  as  are  resolved 
into  forces  expended  by  the  organism;  so,  too,  does  the  non- 
nitrogenous  matter.  Or  perhaps  the  concomitants  of  this 
metamorphosis  of  non-nitrogenous  matter  vary  with  the 
conditions.  Heat  alone  may  result  when  it  is  transformed 
while  in  the  circulating  fluids,  but  partly  heat  and  partly 
another  force  when  it  is  transformed  in  some  active  tissue 
that  has  absorbed  it ;  just  as  coal,  though  producing  little  else 
but  heat  as  ordinarily  burnt,  has  its  heat  partially  trans- 
formed into  mechanical  motion  if  burnt  in  a  steam-engine 
furnace.  In  such  case  the  antithesis  of  Liebig  would  be 
reduced  to  this — that  whereas  nitrogenous  substance  is  tis- 
sue-food both  as  material  for  building-up  tissue  and  as  mate- 
rial for  its  function;  non-nitrogenous  substance  is  tissue- 
food  only  as  material  for  function. 

There  can  be  no  doubt  that  this  thermal  re-action  which 
chemical  action  from  moment  to  moment  produces  in  the 
body,  is  from  moment  to  moment  an  aid  to  further  chemical 
action.  We  before  saw  (First  Principles,  §  100)  that  a  state 
of  raised  molecular  vibration  is  favourable  to  those  re-dis- 
tributions of  matter  and  motion  which  constitute  Evolution. 
We  saw  that  in  organisms  distinguished  by  the  amount  and 
rapidity  of  such  re-distributions,  this  raised  state  of  molecular 
vibration  is  conspicuous.  And  we  here  see  that  this  raised 
state  of  molecular  vibration  is  itself  a  continuous  conse- 
quence of  the  continuous  molecular  re-distributions  it  facili- 
tates. The  heat  generated  by  each  increment  of  chemical 
change  makes  possible  the  succeeding  increment  of  chemical 


THE  RE-ACTIONS  OF  ORGANIC  MATTER  ON  FORCES.     49 

change.  In  the  body  this  connexion  of  phenomena  is  the 
same  as  we  see  it  to  be  out  of  the  body.  Just  as  in  a  burn- 
•ing  piece  of  wood,  the  heat  given  out  by  the  portion  actually 
combining  with  oxygen,  raises  the  adjacent  portion  to  a  tem- 
perature at  which  it  also  can  combine  with  oxygen;  so,  in  a 
living  animal,  the  heat  produced  by  oxidation  of  each  portion 
of  organized  or  unorganized  substance,  maintains  the  tem- 
perature at  which  the  unoxidized  portions  can  be  readily 
oxidized. 

§  19.  Among  the  forces  called  forth  from  organisms  by 
re-action  against  the  actions  to  which  they  are  subject,  is 
Light.  Phosphorescence  is  in  some  few  cases  displayed  by 
plants — especially  by  certain  fungi.  Among  animals  it  is 
comparatively  common.  All  know  that  there  are  several 
kinds  of  luminous  insects;  and  many  are  familiar  with  the 
fact  that  luminosity  is  a  characteristic  of  various  marine 
creatures. 

Much  of  the  evidence  is  supposed  to  imply  that  this  evolu- 
tion of  light,  like  the  evolution  of  heat,  is  consequent  on 
oxidation  of  the  tissues  or  of  matters  contained  in  them. 
Light,  like  heat,  is  the  expression  of  a  raised  state  of  molecular 
vibration :  the  difference  between  them  being  a  difference  in 
the  rates  of  vibration.  Hence  it  seems  inferable  that  by 
chemical  action  on  substances  contained  in  the  organism,  heat 
or  light  may  be  produced,  according  to  the  character  of  the 
resulting  molecular  vibrations.  Some  experimental  evidence 
supports  this  view.  In  phosphorescent  insects,  the  con- 
tinuance of  the  light  is  found  to  depend  on  the  continuance 
of  respiration;  and  any  exertion  which  renders  respiration 
more  active,  increases  the  brilliancy  of  the  light.  Moreover, 
by  separating  the  luminous  matter,  Prof.  Matteucci  has 
shown  that  its  emission  of  light  is  accompanied  by  absorp- 
tion of  oxygen  and  escape  of  carbonic  acid.  The 
phosphorescence  of  marine  animals  has  been  referred  to 
other  caiises  than  oxidation;  but  it  may  perhaps  be  ex- 


50  THE  DATA  OF  BIOLOGY. 

plicable  without  assuming  any  more  special  agency.  Con- 
sidering that  in  creatures  of  the  genus  Noctiluca,  for  example, 
to  which  the  phosphorescence  most  commonly  seen  on  our* 
own  coasts  is  due,  there  is  no  means  of  keeping  up  a  con- 
stant circulation,  we  may  infer  that  the  movements  of 
aerated  fluids  through  their  tissues,  must  be  greatly  affected 
by  impulses  received  from  without.  Hence  it  may  be  that 
the  sparkles  visible  at  night  when  the  waves  break  gently  on 
the  beach,  or  when  an  oar  is  dipped  into  the  water,  are  called 
forth  from  these  creatures  by  the  concussion,  not  because  of 
any  unknown  influence  it  excites,  but  because,  being  propa- 
gated through  their  delicate  tissues,  it  produces  a  sudden 
movement  of  the  fluids  and  a  sudden  increase  of  chemical 
action. 

Nevertheless,  in  other  phosphorescent  animals  inhabiting 
the  sea,  as  in  the  Pyrosoma  and  in  certain  Annelida,  light 
seems  to  be  produced  otherwise  than  by  direct  re-action  on 
the  action  of  oxygen.  Indeed,  it  needs  but  to  recall  the  now 
familiar  fact  that  certain  substances  become  luminous  in  the 
dark  after  exposure  to  sunlight,  to  see  that  there  are  other 
cattses  of  light-emission. 

§  20.  The  re-distributions  of  inanimate  matter  are  habitu- 
ally accompanied  by  electrical  disturbances;  and  there  is 
abundant  evidence  that  electricity  is  generated  during  those 
re-distributions  of  matter  that  are  ever  taking  place  in 
organisms.  Experiments  have  shown  "that  the  skin  and 
most  of  the  internal  membranes  are  in  opposite  electrical 
states ; "  and  also  that  between  different  internal  organs,  as 
the  liver  and  the  stomach,  there  are  electrical  contrasts :  such 
contrasts  being  greatest  where  the  processes  going  on  in  the 
compared  parts  are  most  unlike.  It  has  been  proved  by 
du  Bois-Reymond  that  when  any  point  in  the  longitudinal 
section  of  a  muscle  is  connected  by  a  conductor  with  any 
point  in  its  transverse  section,  an  electric  current  is  estab- 
lished; and  further,  that  like  results  occur  when  nerves  are 


THE  RE-ACTIONS  OF  ORGANIC  MATTER  ON  FORCES.      51 

substituted  for  muscles.  The  special  causes  of  these  pheno- 
mena have  not  yet  been  determined.  Considering  that  the 
electric  contrasts  are  most  marked  where  active  secretions 
are  going  on — considering,  too,  that  they  are  difficult  to 
detect  where  there  are  no  appreciable  movements  of  liquids 
— considering,  also,  that  even  when  muscles  are  made  to  con- 
tract after  removal  from  the  body,  the  contraction  inevitably 
causes  movements  of  the  liquids  still  contained  in  its  tissues ; 
it  may  be  that  they  are  due  simply  to  the  friction  of  hetero- 
geneous substances,  which  is  universally  a  cause  of  electric 
disturbance.  But  whatever  be  the  interpretation,  the  fact 
remains  the  same: — there  is  throughout  the  living  organism, 
an  unceasing  production  of  differences  between  the  electric 
states  of  different  parts;  and,  consequently,  an  unceasing 
restoration  of  electric  equilibrium  by  the  establishment  of 
currents  among  these  parts. 

Besides  these  general,  and  not  conspicuous,  electrical  phe- 
nomena common  to  all  organisms,  vegetal  as  well  as  animal, 
there  are  certain  special  and  strongly  marked  ones.  I  refer, 
of  course,  to  those  which  have  made  the  Torpedo  and  the 
Gymnotus  objects  of  so  much  interest.  In  these  creatures 
we  have  a  genesis  of  electricity  which  is  not  incidental  on 
the  performance  of  their  different  functions  by  the  different 
organs;  but  one  which  is  itself  a  function,  having  an  organ 
appropriate  to  it.  The  character  of  this  organ  in  both  these 
fishes,  and  its  largely-developed  connexions  with  the  nervous 
centres,  have  raised  in  some  minds  the  suspicion  that  in  it 
there  takes  place  a  transformation  of  what  we  call  nerve- 
force  into  the  force  known  as  electricity.  Perhaps,  however, 
the  true  interpretation  may  rather  be  that  by  nervous  stimu- 
lation there  is  set  up  in  these  animal-batteries  that  particular 
transformation  of  molecular  motion  which  it  is  their  function 
to  produce. 

But  whether  general  or  special,  and  in  whatever  manner 
produced,  these  evolutions  of  electricity  are  among  the  re- 
actions of  organic  matter  called  forth  by  the  actions  to  which 


52  THE  DATA  OP  BIOLOGY. 

it  is  subject.  Though  these  re-actions  are  not  direct,  but 
seem  to  be  remote  consequences  of  changes  wrought  by 
external  agencies  on  the  organism,  they  are  yet  incidents  in 
that  general  re-distribution  of  motion  which  these  external 
agencies  initiate;  and  as  such  must  here  be  noticed. 

§  21.  To  these  known  modes  of  motion,  has  next  to  be 
added  an  unknown  one.  Heat,  Light,  and  Electricity  are 
emitted  by  inorganic  matter  when  undergoing  changes,  as 
well  as  by  organic  matter.  But  there  is  manifested  in  some 
classes  of  living  bodies  a  kind  of  force  which  we  cannot 
identify  with  any  of  the  forces  manifested  by  bodies  that  are 
not  alive, — a  force  which  is  thus  unknown,  in  the  sense  that 
it  cannot  be  assimilated  to  any  otherwise-recognized  class.  I 
allude  to  what  is  called  nerve-force. 

This  is  habitually  generated  in  all  animals,  save  the  lowest, 
by  incident  forces  of  every  kind.  The  gentle  and  violent 
mechanical  contacts,  which  in  ourselves  produce  sensations 
of  touch  and  pressure — the  additions  and  abstractions  of 
molecular  vibration,  which  in  ourselves  produce  sensations  of 
heat  and  cold,  produce  in  all  creatures  that  have  nervous 
systems,  certain  nervous  disturbances:  disturbances  which, 
as  in  ourselves,  are  either  communicated  to  the  chief  nervous 
centre,  and  there  arouse  consciousness,  or  else  result  in  mere 
physical  processes  set  going  elsewhere  in  the  organism.  In 
special  parts  distinguished  as  organs  of  sense,  other  external 
actions  bring  about  other  nervous  re-actions,  that  show  them- 
selves either  as  special  sensations  or  as  excitements  which, 
without  the  intermediation  of  distinct  consciousness,  beget 
actions  in  muscles  or  other  organs.  Besides  neural 

discharges  following  the  direct  incidence  of  external  forces, 
others  are  ever  being  caused  by  the  incidence  of  forces 
which,  though  originally  external,  have  become  internal  by 
absorption  into  the  organism  of  the  agents  exerting  them. 
For  thus  may  be  classed  those  neural  discharges  which  result 
from  modifications  of  the  tissues  wrought  by. substances  car- 


THE  RE-ACTIONS  OP  ORGANIC  MATTER  ON  FORCES.      53 

ried  to  them  in  the  blood.  That  the  unceasing  change  of 
matter  which  oxygen  and  other  agents  produce  throughout 
the  system,  is  accompanied  by  production  of  nerve-force,  is 
shown  by  various  facts; — by  the  fact  that  nerve-force  is  no 
longer  generated  if  oxygen  be  withheld  or  the  blood  pre- 
vented from  circulating;  by  the  fact  that  when  the  chemical 
transformation  is  diminished,  as  during  sleep  with  its  slow 
respiration  and  circulation,  there  is  a  diminution  in  the 
quantity  of  nerve-force;  by  the  fact  that  an  excessive  ex- 
penditure of  nerve-force  involves  excessive  respiration  and 
circulation,  and  excessive  waste  of  tissue.  To  these  proofs 
that  nerve-force  is  evolved  in  greater  or  less  quantity,  accord- 
ing as  the  conditions  to  rapid  molecular  change  throughout 
the  body  are  well  or  ill  fulfilled,  may  be  added  proofs  that 
certain  special  molecular  actions  are  the  causes  of  these 
special  re-actions.  The  effects  of  the  vegeto-alkalies  put 
beyond  doubt  the  inference  that  the  overthrow  of  molecular 
equilibrium  by  chemical  affinity,  when  it  occurs  in  certain 
parts,  causes  excitement  in  the  nerves  proceeding  from  those 
parts.  Indeed,  looked  at  from  this  point  of  view,  the 

two  classes  of  nervous  changes — the  one  initiated  from  with- 
out and  the  other  from  within — are  seen  to  merge  into  one 
class.  Both  of  them  may  be  traced  to  metamorphosis  of 
tissue.  The  sensations  of  touch  and  pressure  are  doubtless 
consequent  on  accelerated  changes  of  matter,  produced  by 
mechanical  disturbance  of  the  mingled  fluids  and  solids  com- 
posing the  parts  affected.  There  is  abundant  evidence  that 
the  gustatory  sensation  is  due  to  the  chemical  actions  set  up 
by  particles  which  find  their  way  through  the  membrane 
covering  the  nerves  of  taste ;  for,  as  Prof.  Graham  points  out, 
sapid  substances  belong  to  the  class  of  crystalloids,  which 
are  able  rapidly  to  permeate  animal  tissue,  while  the  colloids 
which  cannot  pass  through  animal  tissue  are  insipid.  Simi- 
larly with  the  sense  of  smell.  Substances  which  excite  this 
sense  are  necessarily  more  or  less  volatile;  and  their  vola- 
tility being  the  result  of  their  molecular  mobility,  implies 
5 


54  THE  DATA  OP  BIOLOGY. 

that  they  have,  in  a  high  degree,  the  power  of  getting  at  the 
olfactory  nerves  by  penetrating  their  mucous  investment. 
Again,  the  facts  which  photography  has  familiarized  us  with, 
show  that  those  nervous  impressions  called  colours,  are 
primarily  due  to  certain  changes  wrought  by  light  in  the 
substance  of  the  retina.  And  though,  in  the  case  of  hearing, 
we  cannot  so  clearly  trace  the  connexion  of  cause  and  effect, 
yet  as  we  see  that  the  auditory  apparatus  is  one  fitted  to 
intensify  those  vibrations  constituting  sound,  and  to  convey 
them  to  a  receptacle  containing  liquid  in  which  nerves  are 
immersed,  it  can  scarcely  be  doubted  that  the  sensation  of 
sound  proximately  results  from  molecular  re-arrangements 
caused  in  these  nerves  by  the  vibrations  of  the  liquid :  know- 
ing, as  we  do,  that  the  re-arrangement  of  molecules  is  in  all 
cases  aided  by  agitation.  Perhaps,  however,  the  best 

proof  that  nerve-force,  whether  peripheral  or  central  in 
origin,  results  from  chemical  change,  lies  in  the  fact  that 
most  of  the  chemical  agents  which  powerfully  affect  the 
nervous  system,  affect  it  whether  applied  at  the  centre  or 
at  the  periphery.  Various  mineral  acids  are  tonics — the 
stronger  ones  being  usually  the  stronger  tonics;  and  this 
which  we  call  their  acidity  implies  a  power  in  them  of  act- 
ing on  the  nerves  of  taste,  while  the  tingling  or  pain  fol- 
lowing their  absorption  through  the  skin,  implies  that  the 
nerves  of  the  skin  are  acted  on  by  them.  Similarly  with 
certain  vegeto-alkalies  which  are  peculiarly  bitter.  By  their 
bitterness  these  show  that  they  affect  the  extremities  of  the 
nerves,  while,  by  their  tonic  properties,  they  show  that  they 
affect  the  nervous  centres:  the  most  intensely  bitter  among 
them,  strychnia,  being  the  most  powerful  nervous  stimulant.* 
However  true  it  may  be  that  this  relation  is  not  a  regular 
one,  since  opium,  hashish,  and  some  other  drugs,  which  work 

*  When  writing  this  passage  I  omitted  to  observe  the  verification  yielded 
of  the  conclusion  contained  in  §  15  concerning  the  part  played  in  the  vital 
processes  by  the  nitrogenous  compounds.  For  these  vegeto-alkalies,  minute 
quantities  of  which  produce  such  great  effects  in  exalting  the  functions  (e.  g., 
a  sixteenth  of  a  grain  of  strychnia  is  a  dose),  are  all  nitrogenous  bodies,  and, 


THE   RE-ACTIONS  OF  ORGANIC  MATTER  ON  FORCES.      55 

marked  effects  on  the  brain,  are  not  remarkably  sapid — how- 
ever true  it  may  be  that  there  are  relations  between  par- 
ticular substances  and  particular  parts  of  the  nervous  system ; 
yet  such  instances  do  but  qualify,  without  negativing,  the 
general  proposition.  The  truth  of  this  proposition  can 
scarcely  be  doubted  when,  to  the  facts  above  given,  is  added 
the  fact  that  various  condiments  and  aromatic  drugs  act  as 
nervous  stimulants;  and  the  fact  that  anaesthetics,  besides 
the  general  effects  they  produce  when  inhaled  or  swallowed, 
produce  local  effects  of  like  kind — first  stimulant  and  then 
sedative — when  absorbed  through  the  skin;  and  the  fact  that 
ammonia,  which  in  consequence  of  its  extreme  molecular 
mobility  so  quickly  and  so  violently  excites  the  nerves  be- 
neath the  skin,  as  well  as  those  of  the  tongue  and  the  nose, 
is  a  rapidly-acting  stimulant  when  taken  internally. 

Whether  a  nerve  is  merely  a  conductor,  which  delivers  at 
one  of  its  extremities  an  impulse  received  at  the  other,  or 
whether,  as  some  now  think,  it  is  itself  a  generator  of  force 

by  implication,  relatively  unstable  bodies.  The  small  amounts  of  molecular 
change  which  take  place  in  these  small  quantities  of  the  vegeto-alkalies  when 
diffused  through  the  system,  initiate  larger  amounts  of  molecular  change  in 
the  nitrogenous  elements  of  the  tissues. 

But  the  evidence  furnished  a  generation  ago  by  these  vegeto-alkalies  has 
been  greatly  reinforced  by  far  more  striking  evidence  furnished  by  other 
nitrogenous  compounds — the  various  explosives.  These,  at  the  same  time 
that  they  produce  by  their  sudden  decompositions  violent  effects  outside  the 
organism,  also  produce  violent  effects  inside  it :  a  hundredth,  of  a  grain  of 
nitro-glycerine  being  a  sufficient  dose.  Investigations  made  by  Dr.  J.  B. 
Bradbury,  and  described  by  him  in  the  Bradshaw  Lecture  on  "Some  New 
Vaso-Dilators  "  (see  TJie  Lancet,  Nov.  16,  1895),  details  the  effects  of  kindred 
bodies — methyl-nitrate,  glycol-dinitrate,  erythrol-tetranitrate.  The  first  two, 
in  common  with  nitro-glycerine,  are  stable  only  when  cool  and  in  the  dark — 
sunlight  or  warmth  decomposes  them,  and  they  explode  by  rapid  heating  or 
percussion.  The  fact  which  concerns  us  here  is  that  the  least  stable — glycol- 
dinitrate — has  the  most  powerful  and  rapid  physiological  effect,  which  is  pro- 
portionately transient.  In  one  minute  the  blood-pressure  is  reduced  by  one- 
fourth  and  in  four  minutes  by  nearly  two-thirds :  an  effect  which  is  dissipated 
in  a  quarter  of  an  hour.  So  that  this  excessively  unstable  compound,  decom- 
posing in  the  body  in  a  very  short  time,  produces  within  that  short  time  a  vast 
amount  of  molecular  change:  acting,  as  it  seems,  not  through  the  nervous 
system,  but  directly  on  the  blood-vessels. 


50  THE  DATA  OF  BIOLOGY. 

which  is  initiated  at  one  extremity  and  accumulates  in  its 
course  to  the  other  extremity,  are  questions  which  cannot 
vet  be  answered.  All  we  know  is  that  agencies  capable  of 
working  molecular  changes  in  nerves  are  capable  of  calling 
forth  from  them  manifestations  of  activity.  And  our  evi- 
dence that  nerve-force  is  thus  originated,  consists  not  only  of 
such  facts  as  the  above,  but  also  of  more  conclusive  facts 
established  by  direct  experiments  on  nerves — experiments 
which  show  that  nerve-force  results  when  the  cut  end  of  a 
nerve  is  either  mechanically  irritated,  or  acted  on  by  some 
chemical  agent,  or  subject  to  the  galvanic  current — experi- 
ments which  prove  that  nerve-force  is  generated  by  whatever 
disturbs  the  molecular  equilibrium  of  nerve-substance. 

§  22.  The  most  important  of  the  re-actions  called  forth 
from  organisms  by  surrounding  actions,  remains  to  be  noticed. 
To  the  various  forms  of  insensible  motion  thus  caused,  we 
have  to  add  sensible  motion.  On  the  production  of  this 
mode  of  force  more  especially  depends  the  possibility  of  all 
vital  phenomena.  It  is,  indeed,  usual  to  regard  the  power  of 
generating  sensible  motion  as  confined  to  one  out  of  the  two 
organic  sub-kingdoms;  or,  at  any  rate,  as  possessed  by  but 
few  members  of  the  other.  On  looking  closer  into  the  matter, 
however,  we  see  that  plant-life  as  well  as  animal-life,  is  uni- 
versally accompanied  by  certain  manifestations  of  this  power; 
and  that  plant-life  could  not  otherwise  continue. 

Through  the  humblest,  as  well  as  through  the  highest, 
vegetal  organisms,  there  are  ever  going  on  certain  re-distri- 
butions of  matter.  In  Protophytes  the  microscope  shows  us 
an  internal  transposition  of  parts,  which,  when  not  imme- 
diately visible,  is  proved  to  exist  by  the  changes  of  arrange- 
ment that  become  manifest  in  the  course  of  hours  and  days. 
In  the  individual  cells  of  many  higher  plants,  an  active 
movement  among  the  contained  granules  may  be  witnessed. 
And  well-developed  cryptogams,  in  common  with  all  phanero- 
gams, exhibit  this  genesis  of  mechanical  motion  still  more 


THE  RE-ACTIONS  OF  ORGANIC  MATTER  ON  FOECES.      5? 

conspicuously  in  the  circulation  of  sap.  It  might,  indeed,  be 
concluded  a  priori,  that  through  plants  displaying  much 
differentiation  of  parts,  an  internal  movement  must  be  going 
on;  since,  without  it,  the  mutual  dependence  of  organs 
having  unlike  functions  would  be  impossible.  Besides 

keeping  up  these  motions  of  liquids  internally,  plants,  espe- 
cially of  the  lower  orders,  move  their  external  'parts  in  rela- 
tion to  each  other,  and  also  move  about  from  place  to  place. 
There  are  countless  such  illustrations  as  the  active  locomo- 
tion of  the  zoospores  of  many  Algce,  the  rhythmical  bendings 
of  the  Oscillatorice,  the  rambling  progression  of  the  Diato- 
macece.  In  fact  many  of  these  smallest  vegetals,  and  many 
of  the  larger  ones  in  their  early  stages,  display  a  mechanical 
activity  not  distinguishable  from  that  of  the  simplest  animals. 
Among  well-organized  plants,  which  are  never  locomotive  in 
their  adult  states,  we  still  not  unfrequently  meet  with  rela- 
tive motions  of  parts.  To  such  familiar  cases  as  those  of  the 
Sensitive  plant  and  the  Venus'  fly-trap,  many  others  may  be 
added.  When  its  base  is  irritated  the  stamen  of  the  Ber- 
berry flower  leans  over  and  touches  the  pistil.  If  the 
stamens  of  the  wild  Cistus  be  gently  brushed  with  the  finger, 
they  spread  themselves :  bending  away  from  the  seed-vessel. 
And  some  of  the  orchid-flowers,  as  Mr.  Darwin  has  shown, 
shoot  out  masses  of  pollen  on  to  the  entering  bee,  when  its 
trunk  is  thrust  down  in  search  of  honey. 

Though  the  power  of  moving  is  not,  as  we  see,  a  character- 
istic of  animals  alone,  yet  in  them,  considered  .as  a  class,  it  is 
manifested  to  an  extent  so  marked  as  practically  to  become 
their  most  distinctive  trait.  For  it  is  by  their  immensely 
greater  ability  to  generate  mechanical  motion,  that  animals 
are  enabled  to  perform  those  actions  which  constitute  their 
visible  lives;  and  it  is  by  their  immensely  greater  ability  to 
generate  mechanical  motion,  that  the  higher  orders  of  animals 
are  most  obviously  distinguished  from  the  lower  orders. 
Though,  on  remembering  the  seemingly  active  movements  of 
infusoria,  some  will  perhaps  question  this  last-named  con- 


58  THE   DATA   OF  BIOLOGY. 

trast,  yet,  on  comparing  the  quantities  of  matter  propelled 
through  given  spaces  in  given  times,  they  will  see  that  the 
momentum  evolved  is  far  less  in  the  Protozoa  than  in  the 
Metazoa.  These  sensible  motions  of  animals  are 

effected  in  sundry  ways.  In  the  humblest  forms,  and  even 
in  some  of  the  more  developed  forms  which  inhabit  the 
water,  locomotion  results  from  the  oscillations  of  whip-like 
appendages,  single  or  double,  or  from  the  oscillations  of 
cilia:  the  contractility  resides  in  these  waving  hairs  that 
grow  from  the  surface.  In  many  Coelenterata  certain  elonga- 
tions or  tails  of  ectodermal  or  endodcrmal  cells  shorten  when 
stimulated,  and  by  these  rudimentary  contractile  organs  the 
movements  are  effected.  In  all  the  higher  animals,  however, 
and  to  a  smaller  degree  in  many  of  the  lower,  sensible 
motion  is  generated  by  a  special  tissue,  under  a  special  ex- 
citement. Though  it  is  not  strictly  true  that  such  animals 
show  no  sensible  motions  otherwise  caused,  since  all  of  them 
have  certain  ciliated  membranes,  and  since  the  circulation 
of  liquids  in  them  is  partially  due  to  osmotic  and  capillary 
actions ;  yet,  generally  speaking,  we  may  say  that  their  move- 
ments are  effected  solely  by  muscles  which  contract  solely 
through  the  agency  of  nerves. 

What  special  transformations  of  force  generate  these  vari- 
ous mechanical  changes,  we  do  not,  in  most  cases,  know. 
Those  re-distributions  of  liquid,  with  the  alterations  of  form 
sometimes  caused  by  them,  that  result  from  osmose,  are  not, 
indeed,  incomprehensible.  Certain  motions  of  plants  which, 
like  those  of  the  "  animated  oat,"  follow  contact  with  water, 
are  easily  interpreted;  as  are  also  such  other  vegetal  motions 
as  those  of  the  Touch-me-not,  the  Squirting  Cucumber,  and 
the  Carpobolus.  But  we  are  ignorant  of  the  mode  in  which 
molecular  movement  is  transformed  into  the  movement  of 
masses,  in  animals.  We  cannot  refer  to  known  causes  the 
rhythmical  action  of  a  Medusa's  disc,  or  that  slow  decrease  of 
bulk  which  spreads  throughout  the  mass  of  an  Alcyonium 
when  one  of  its  component  individuals  has  been  irritated. 


THE  RE-ACTIONS  OF  ORGANIC  MATTER  ON   FORCES.      50 

Xor  are  we  any  better  able  to  say  how  the  insensible  motion 
transmitted  through  a  nerve,  gives  rise  to  sensitive  motion  in 
a  muscle.  It  is  true  that  Science  has  given  to  Art  several 
methods  of  changing  insensible  into  sensible  motion.  By 
applying  heat  to  water  we  vaporize  it,  and  the  movement  of 
its  expanding  vapour  we  transfer  to  solid  matter;  but 
evidently  the  genesis  of  muscular  movement  is  in  no 
way  analogous  to  this.  The  force  evolved  in  a  galvanic 
battery  or  by  a  dynamo,  we  communicate  to  a  soft  iron 
magnet  through  a  wire  coiled  round  it;  and  it  would 
be  possible,  by  placing  near  to  each  other  several  magnets 
thus  excited,  to  obtain,  through  the  attraction  of  each  for  its 
neighbours,  an  accumulated  movement  made  up  of  their 
separate  movements,  and  thus  mechanically  to  imitate  a 
muscular  contraction.  But  from  what  we  know  of  organic 
matter  there  is  no  reason  to  suppose  that  anything  analogous 
to  this  takes  place  in  it.  We  can,  however,  through 

one  kind  of  molecular  change,  produce  sensible  changes  of 
aggregation  such  as  possibly  might,  when  occurring  in  organic 
substance,  cause  sensible  motion  in  it.  I  refer  to  change 
that  is  allotropic  or  isomeric.  Sulphur,  for  example,  as- 
sumes different  crystalline  and  non-crystalline  forms  at  dif- 
ferent temperatures,  and  may  be  made  to  pass  backwards 
and  forwards  from  one  form  to  another,  by  slight  variations 
of  temperature :  undergoing  each  time  an  alteration  of  bulk. 
We  know  that  this  allotropism,  or  rather  its  analogue  iso- 
merism,  prevails  among  colloids — inorganic  and  organic.  We 
also  know  that  some  of  these  metamorphoses  among  colloids 
are  accompanied  by  visible  re-arrangements :  instance  hy- 
drated  silicic  acid,  which,  after  passing  from  its  soluble 
state  to  the  state  of  an  insoluble  jelly,  begins,  in  a  few  days, 
to  contract  and  to  give  out  part  of  its  contained  water.  Now 
considering  that  such  isomeric  changes  of  organic  as  well  as 
inorganic  colloids,  are  often  rapidly  produced  by  very  slight 
causes — a  trace  of  a  neutral  salt  or  a  degree  or  two  rise  of 
temperature — it  seems  not  impossible  that  some  of  the  col- 


60  THE  DATA  OF  BIOLOGY. 

loids  constituting  muscle  may  be  thus  changed  by  a  nervous 
discharge:  resuming  their  previous  condition  when  the  dis- 
charge ceases.  Arid  it  is  conceivable  that  by  structural 
arrangements,  minute  sensible  motions  so  caused  may  be 
accumulated  into  large  sensible  motions. 

§  23.  But  the  truths  which  it  is  here  our  business  espe- 
cially to  note,  are  independent  of  hypotheses  or  interpreta- 
tions. It  is  sufficient  for  the  ends  in  view,  to  observe  that 
organic  matter  does  exhibit  these  several  conspicuous  re- 
actions when  acted  on  by  incident  forces.  It  is  not  requisite 
that  we  should  know  how  these  re-actions  originate. 

In  the  last  chapter  were  set  forth  the  several  modes  in 
which  incident  forces  cause  re-distributions  of  organic  matter ; 
and  in  this  chapter  have  been  set  forth  the  several  modes  in 
which  is  manifested  the  motion  accompanying  this  re-distri- 
bution. There  we  contemplated,  under  its  several  aspects, 
the  general  fact  that,  in  consequence  of  its  extreme,  instability, 
organic  matter  undergoes  extensive  molecular  re-arrange- 
ments on  very  slight  changes  of  conditions.  And  here  we  have 
contemplated,  under  its  several  aspects,  the  correlative  general 
fact  that,  during  these  extensive  molecular  re-arrangements, 
there  are  evolved  large  amounts  of  energy.  In  the  one 
case  the  components  of  organic  matter  are  regarded  as  fall- 
ing from  positions  of  unstable  equilibrium  to  positions  of 
stable  equilibrium;  and  in  the  other  case  they  are  regarded 
as  giving  out  in  their  falls  certain  momenta — momenta  that 
may  be  manifested  as  heat,  light,  electricity,  nerve-force,  or 
mechanical  motion,  according  as  the  conditions  determine. 

I  will  add  only  that  these  evolutions  of  energy  are  rigor- 
ously dependent  on  these  changes  of  matter.  It  is  a  corollary 
from  the  primordial  truth  which,  as  we  have  seen,  underlies 
all  other  truths,  (First  Principles,  §§  62,  189,)  that  whatever 
amount  of  power  an  organism  expends  in  any  shape,  is  the 
correlate  and  equivalent  of  a  power  which  was  taken  into  it 
from  without.  On  the  one  hand,  it  follows  from  the  persist- 


THE  RE-ACTIONS  OF  ORGANIC  MATTER  ON  FORCES.      61 

ence  of  force  that  each  portion  of  mechanical-  or  other  energy 
which  an  organism  exerts,  implies  the  transformation  of  as 
much  organic  matter  as  contained  this  energy  in  a  latent 
state.  And  on  the  other  hand,  it  follows  from  the  persistence 
of  force  that  no  such  transformation  of  organic  matter  con- 
taining this  latent  energy  can  take  place,  without  the  energy 
being  in  one  shape  or  other  manifested. 


CHAPTER  IIIA 

METABOLISM. 

i.  IN  the  early  forties  the  French  chemist  Dumas 
pointed  out  the  opposed  actions  of  the  vegetal  and  animal 
kingdoms:  the  one  having  for  its  chief  chemical  effect  the 
decomposition  of  carbon-dioxide,  with  accompanying  assimila- 
tion of  its  carbon  and  liberation  of  its  oxygen,  and  the  other 
having  for  its  chief  chemical  effect  the  oxidation  of  carbon  and 
production  of  carbon-dioxide.  Omitting  those  plants  which 
contain  no  chlorophyll,  all  others  de-oxidize  carbon ;  while  all 
animals,  save  the  few  which  contain  chlorophyll,  re-oxidize 
carbon.  This  is  not,  indeed,  a  complete  account  of  the  general 
relation;  since  it  represents  animals  as  wholly  dependent  on 
plants,  either  directly  or  indirectly  through  other  animals, 
while  plants  are  represented  as  wholly  independent  of  ani- 
mals; and  this  last  representation  though  mainly  true,  since 
plants  can  obtain  direct  from  the  inorganic  world  certain 
other  constituents  they  need,  is  in  some  measure  not  true, 
since  many  with  greater  facility  obtain  these  materials  from 
the  decaying  bodies  of  animals  or  from  their  excreta.  But 
after  noting  this  qualification  the  broad  antithesis  remains  as 
alleged. 

How  are  these  transformations  brought  about?  The  car- 
bon contained  in  carbon-dioxide  does  not  at  a  bound  become 
incorporated  in  the  plant,  nor  does  the  substance  appropriated 
by  the  animal  from  the  plant  become  at  a  bound  carbon- 
dioxide.  It  is  through  two  complex  sets  of  changes  that 


METABOLISM.  63 

these  two  ultimate  results  are  brought  about.  The  materials 
forming  the  tissues  of  plants  as  well  as  the  materials  con- 
tained in  them,  are  progressively  elaborated  from  the  inor- 
ganic substances;  and  the  resulting  compounds,  eaten  and 
some  of  them  assimilated  by  animals,  pass  through  successive 
changes  which  are,  on  the  average,  of  an  opposite  character: 
the  two  sets  being  constructive  and  destructive.  To  express 
changes  of  both  these  natures  the  term  "  metabolism "  is 
used ;  and  such  of  the  metabolic  changes  as  result  in  building 
up  from  simple  to  compound  are  distinguished  as  "  anabolic," 
while  those  which  result  in  the  falling  down  from  compound 
to  simple  are  distinguished  as  "  katabolic."  These  antithetical 
names  do  not  indeed  cover  all  the  molecular  transformations 
going  on.  Many  of  them,  known  as  isomeric,  imply  neither 
building  up  nor  falling  down:  they  imply  re-arrangement 
only.  But  those  which  here  chiefly  concern  us  are  the  two 
opposed  kinds  described. 

A  qualification  is  needful.  These  antithetic  changes  must 
be  understood  as  characterizing  plant-life  and  animal-life  in 
general  ways  rather  than  in  special  ways — as  expressing 
the  transformations  in  their  totalities  but  not  in  their  details. 
For  there  are  katabolic  processes  in  plants,  though  they  bear 
but  a  small  ratio  to  the  anabolic  ones ;  and  there  are  anabolic 
processes  in  animals,  though  they  bear  but  a  small  ratio  to 
the  katabolic  ones. 

From  the  chemico-physical  aspect  of  these  changes  we 
pass  to  those  distinguished  as  vital;  for  metabolic  changes 
can  be  dealt  with  only  as  changes  effected  by  that  living 
substance  called  protoplasm. 

§  23&.  On  the  evolution-hypothesis  we  are  obliged  to  as- 
sume that  the  earliest  living  things — probably  minute  units' 
of  protoplasm  smaller  than  any  the  microscope  reveals  to 
us — had  the  ability  to  appropriate  directly  from  the  inor- 
ganic world  both  the  nitrogen  and  the  materials  for  carbo- 
hydrates without  both  of  which  protoplasm  cannot  be  formed ; 


64  THE   DATA  OF  BIOLOGY. 

since  in  the  absence  of  preceding  organic  matter  there  was 
no  other  source.  The  general  law  of  evolution  as  well  as  the 
observed  actions  of  Protozoa  and  Protophyta,  suggest  that 
these  primordial  types  simultaneously  displayed  animal-life 
and  plant-life.  For  whereas  the  developed  animal-type 
cannot  form  from  its  inorganic  surroundings  either  nitro- 
genous compounds  or  carbo-hydrates;  and  whereas  the  de- 
veloped plant-type,  able  to  form  carbo-hydrates  from  its  in- 
organic surroundings,  depends  for  the  formation  of  its  pro- 
toplasm mainly,  although  indirectly,  on  the  nitrogenous 
compounds  derived  from  preceding  organisms,  as  do  also  most 
of  the  plants  devoid  of  chlorophyll — the  fungi ;  we  are  obliged 
to  assume  that  in  the  beginning,  along  with  the  expending 
activities  characterizing  the  animal-type,  there  went  the  ac- 
cumulating activities  characterizing  both  of  the  vegetal  types 
— forms  of  activity  by-and-by  differentiated. 

Though  the  successive  steps  in  the  artificial  formation  of 
organic  compounds  have  now  gone  so  far  that  substances 
simulating  proteids,  if  not  identical  with  them,  have  been 
produced,  yet  we  have  no  clue  to  the  conditions  under  which 
proteids  arose;  and  still  less  have  we  a  clue  to  the  conditions 
under  which  inert  proteids  became  so  combined  as  to  form 
active  protoplasm.  The  essential  fact  to  be  recognized  is 
that  living  matter,  originated  as  we  must  assume  during  a 
long  stage  of  progressive  cooling  in  which  the  infinitely  varied 
parts  of  the  Earth's  surface  were  slowly  passing  through  ap- 
propriate physical  conditions,  possessed  from  the  outset  the 
power  of  assimilating  to  itself  the  materials  from  which 
more  living  matter  was  formed;  and  that  since  then  all  liv- 
ing matter  has  arisen  from  its  self-increasing  action.  But 
now,  leaving  speculation  concerning  these  anabolic  changes 
as  they  commenced  in  the  remote  past,  let  us  contemplate 
them  as  they  are  carried  on  now — first  directing  our  atten- 
tion to  those  presented  in  the  vegetal  world. 

§  23c.  The  decomposition  of  carbon-dioxide  (§  13)— the 


METABOLISM.  65 

separation  of  its  carbon  from  the  combined  oxygen  so  that 
it  may  enter  into  one  or  other  form  of  carbo-hydrate, — is  not 
now  ordinarily  effected,  as  we  must  assume  it  once  was,  by 
the  undifferentiated  protoplasm;  but  is  effected  by  a 
specialized  substance,  chlorophyll,  imbedded  in  the  proto- 
plasm and  operating  by  its  instrumentality.  The  chloro- 
phyll-grain is  not  simply  immersed  in  protoplasm  but  is 
permeated  throughout  its  substance  by  a  protoplasmic  net- 
work or  sponge-work  apparently  continuous  with  the  proto- 
plasm around ;  or,  according  to  Sachs,  consists  of  protoplasm 
holding  chlorophyll-particles  in  suspension:  the  mechanical 
arrangement  facilitating  the  chemical  function.  The  result- 
ing abstraction  of  carbon  from  carbon-dioxide,  by  the  aid  of 
certain  ethereal  undulations,  appears  to  be  the  first  step  in 
the  building  up  of  organic  compounds — the  first  step  in  the 
primary  anabolic  process.  We  are  not  here  concerned  with 
details.  Two  subsequent  sets  of  changes  only  need  here  to 
be  noted — the  genesis  of  the  passive  materials  out  of  which 
plant-structure  is  built  up,  and  the  genesis  of  the  active  mate- 
rials by  which  these  are  produced  and  the  building  up  effected. 
The  hydrated  carbon  which  protoplasm,  having  the  chloro- 
phyll-grain as  its  implement,  produces  from  carbonic  acid 
and  water,  appears  not  to  be  of  one  kind  only.  The  possible 
carbo-hydrates  are  almost  infinite  in  number.  Multitudes  of 
them  have  been  artificially  made,  and  numerous  kinds  are 
made  naturally  by  plants.  Though  perhaps  the  first  step  in 
the  reduction  of  the  carbon  from  its  dioxide  may  be  always 
the  same,  yet  it  is  held  probable  that  in  different  types  of 
plants  different  types  of  carbo-hydrates  forthwith  arise,  and 
give  differential  characters  to  the  compounds  subsequently 
formed  by  such  types :  sundry  of  the  changes  being  katabolic 
rather  than  anabolic.  Of  leading  members  in  the  group 
may  be  named  dextrin,  starch,  and  the  various  sugars 
characteristic  of  various  plants,  as  well  as  the  cellulose 
elaborated  by  further  anabolism.  Considered  as  the  kind  of 
carbo-hydrate  in  which  the  products  of  activity  are  first  stored 


66  THE  DATA  OP  BIOLOGY. 

up,  to  be  subsequently  modified  for  divers  purposes,  starch  is 
the  most  important  of  these;  and  the  process  of  storage  is 
suggested  by  the  structure  of  the  starch-grain.  This  con- 
sists of  superposed  layers,  implying  intermittent  deposits: 
the  probability  being  that  the  variations  of  light  and  heat 
accompanying  day  and  night  are  associated  now  with  arrest 
of  the  deposit  and  now  with  recommencement  of  it.  Like 
in  composition  as  this  stored-up  starch  is  with  sugar  of  one 
or  other  kind,  and  capable  of  being  deposited  from  sugar  and 
again  assuming  the  sugar  form,  this  substance  passes,  by 
further  metabolism,  here  into  the  cellulose  which  envelopes 
each  of  the  multitudinous  units  of  protoplasm,  there  into  the 
spiral  fibres,  annuli,  or  fenestrated  tubes  which,  in  early  stages 
of  tissue-growth,  form  channels  for  the  sap,  and  elsewhere 
into  other  components  of  the  general  structure.  The  many 
changes  implied  are  effected  in  various  ways :  now  by  that 
simple  re-arrangement  of  components  known  as  isomeric 
change;  now  by  that  taking  from  a  compound  one  of  its  ele- 
ments and  inserting  one  of  another  kind,  which  is  known  as 
substitution ;  and  now  by  oxidation,  as  when  the  oxy-cellulose 
which  constitutes  wood-fibre,  is  produced. 

Besides  elaborating  building  materials,  the  protoplasm 
elaborates  itself — that  is,  elaborates  more  of  itself.  It  is 
chemically  distinguished  from  the  building  materials  by  the 
presence  of  nitrogen.  Derived  from  atmospheric  ammonia, 
or  from  decaying  or  excreted  organic  matter,  or  from  the 
products  of  certain  fungi  and  microbes  at  its  roots,  the  nitro- 
gen in  one  or  other  combination  is  brought  into  a  plant  by 
the  upward  current;  and  by  some  unknown  process  (not 
dependent  on  light,  since  it  goes  on  equally  well  if  not  better 
in  darkness)  the  protoplasm  dissociates  and  appropriates 
this  combined  nitrogen  and  unites  it  with  a  carbo-hydrate 
to  form  one  or  other  proteid — albumen,  gluten,  or  some 
isomer;  appropriating  at  the  same  time  from  certain  of  the 
earth-salts  the  requisite  amount  of  sulphur  and  in  some  cases 
phosphorus.  The  ultimate  step,  as  we  must  suppose,  is  the 


METABOLISM.  6T 

formation  of  living  protoplasm  out  of  these  non-living  pro- 
teids.  A  cardinal  fact  is  that  proteids  admit  of  multi- 
tudinous transformations;  and  it  seems  not  improbable  that 
in  protoplasm  various  isomeric  proteids  are  mingled.  If  so, 
we  must  conclude  that  protoplasm  admits  of  almost  infinite 
variations  in  nature.  Of  course  pari  passu  with  this  dual 
process — augmentation  of  protoplasm  and  accompanying 
production  of  carbo-hydrates — there  goes  extension  of  plant- 
structure  and  plant-life. 

To  these  essential  metabolic  processes  have  to  be  added 
certain  ancillary  and  non-essential  ones,  ending 'in  the  forma- 
tion of  colouring  matters,  odours,  essential  oils,  acrid  secre- 
tions, bitter  compounds  and  poisons :  some  serving  to  attract 
animals  and  others  to  repel  them.  Sundry  of  these  appear 
to  be  excretions — useless  matters  cast  out,  and  are  doubtless 
katabolic. 

The  relation  of  these  facts  here  sketched  in  rude  outline 
to  the  doctrine  of  Evolution  at  large  should  be  observed. 
Already  we  have  seen  how  (§  8a),  in  the  course  of  terrestrial 
evolution,  there  has  been  an  increasingly  heterogeneous  as- 
semblage of  increasing  heterogeneous  compounds,  preparing 
the  way  for  organic  life.  And  here  we  may  see  that  during 
the  development  of  plant-life  from  its  lowest  algoid  and  fun- 
goid forms  up  to  those  forms  which  constitute  the  chief 
vegetal  world,  there  has  been  an  increasing  number  of  com- 
plex organic  compounds  formed;  displayed  at  once  in  the 
diversity  of  them  contained  in  the  same  plant  and  in  the 
still  greater  diversity  displayed  in  the  vast  aggregate  of 
species,  genera,  orders,  and  classes  of  plants. 

§  23d.  On  passing  to  the  metabolism  characterizing  ani- 
mal life,  which,  as  already  indicated,  is  in  the  main  a  process 
of  decomposition  undoing  the  process  of  composition  charac- 
terizing vegetal  life,  we  may  fitly  note  at  the  outset  that  it 
must  have  wide  limits  of  variation,  alike  in  different  classes 
of  animals  and  even  in  the  same  animal. 


flg  THE  DATA  OF  BIOLOGY. 

If  we  take,  on  the  one  hand,  a  carnivore  living  on  muscu- 
lar tissue  (for  wild  carnivores  preying  upon  herbivores  which 
can  rarely  become  fat  obtain  scarcely  any  carbo-hydrates) 
and  observe  that  its  food  is  almost  exclusively  nitrogenous; 
and  if,  on  the  other  hand,  we  take  a  graminivorous  animal 
the  food  of  which  (save  when  it  eats  seeds)  contains  com- 
paratively little  nitrogenous  matter;  we  seem  obliged  to  sup- 
pose that  the  parts  played  in  the  organic  processes  by  the 
proteids  and  the  carbo-hydrates  can  in  considerable  measures 
replace  one  another.  It  is  true  that  the  quantity  of  food 
and  the  required  alimentary  system  in  the  last  case,  are  very 
much  greater  than  in  the  first  case.  But  this  difference  is 
mainly  due  to  the  circumstance  that  the  food  of  the  gramin- 
ivorous animal  consists  chiefly  of  waste-matter — ligneous 
fibre,  cellulose,  chlorophyll — and  that  could  the  starch,  sugar, 
and  protoplasm  be  obtained  without  the  waste-matter,  the 
required  bulks  of  the  two  kinds  of  food  would  be  by  no 
means  so  strongly  contrasted.  This  becomes  manifest  on 
comparing  flesh-eating  and  grain-eating  birds — say  a  hawk 
and  a  pigeon.  In  powers  of  flight  these  do  not  greatly 
differ,  nor  is  the  size  of  the  alimentary  system  conspicuously 
greater  in  the  last  than  in  the  first;  though  probably  the 
amount  of  food  consumed  is  greater.  Still  it  seems  clear 
that  the  supply  of  energy  obtained  by  a  pigeon  from  carbo- 
hydrates with  a  moderate  proportion  of  proteids  is  not  widely 
unlike  that  obtained  by  a  hawk  from  proteids  alone.  Even 
from  the  traits  of  men  differently  fed  a  like  inference  may  be 
drawn.  On  the  one  hand  we  have  the  Masai  who,  during 
their  warrior-days,  eat  flesh  exclusively;  and  on  the  other 
hand  we  have  the  Hindus,  feeding  almost  wholly  on  vege- 
table food.  Doubtless  the  quantities  required  in  these  cases 
differ  much;  but  the  difference  between  the  rations  of  the 
flesh-eater  and  the  grain-eater  is  not  so  immense  as  it  would 
be  were  there  no  substitution  in  the  physiological  uses  of  the 
materials. 

Concerning  the  special  aspects  of  animal-metabolism,  we 


METABOLISM.  69 

have  first  to  note  those  various  minor  transformations  that 
are  auxiliary  to  the  general  transformation  by  which  force  is 
obtained  from  food.  For  many  of  the  vital  activities  merely 
subserve  the  elaboration  of  materials  for  activity  at  large, 
and  the  getting  rid  of  waste  products.  From  blood  passing 
through  the  salivary  glands  is  prepared  in  large  quantity  a 
secretion  containing  among  other  matters  a  nitrogenous  fer- 
ment, ptyaline,  which,  mixed  with  food  during  mastication, 
furthers  the  change  of  its  starch  into  sugar.  Then  in  the 
stomach  come  the  more  or  less  varying  secretions  known  in 
combination  as  gastric  juice.  Besides  certain  salts  and 
hydrochloric  acid,  this  contains  another  nitrogenous  ferment, 
pepsin,  which  is  instrumental  in  dissolving  the  proteids 
swallowed.  To  these  two  metabolic  products  aiding  solution 
of  the  various  ingested  solids,  is  presently  added  that  pro- 
duct of  metabolism  in  the  pancreas  which,  added  to  the 
chyme,  effects  certain  other  molecular  changes — notably  that 
of  such  amylaceous  matters  as  are  yet  unaltered,  into  sac- 
charine matters  to  be  presently  absorbed.  And  let  us  note 
the  significant  fact  that  the  preparation  of  food-materials  in 
the  alimentary  canal,  again  shows  us  that  unstable  nitrogenous 
compounds  are  the  agents  which,  while  themselves  changing, 
set  up  changes  in  the  carbo-hydrates  and  proteids  around: 
the  nitrogen  plays  the  same  part  here  as"  elsewhere.  It  does 
the  like  in  yet  another  viscus.  Blood  which  passes  through 
the  spleen  on  its  way  to  the  liver,  is  exposed  to  the  action 
of  "  a  special  proteid  of  the  nature  of  alkali-albumin,  hold- 
ing iron  in  some  way  peculiarly  associated  with  it."  Lastly 
we  come  to  that  all-important  organ  the  liver,  at  once  a 
factory  and  a  storehouse.  Here  several  metabolisms  are 
simultaneously  carried  on.  There  is  that  which  until  recent 
years  was  supposed  to  be  the  sole  hepatic  process — the 
formation  of  bile.  In  some  liver-cells  are  masses  of  oil- 
globules,  which  seem  to  imply  a  carbo-hydrate  metamor- 
phosis. And  then,  of  leading  importance,  comes  the  exten- 
sive production  of  that  animal-starch  known  as  glycogen — a 


70  THE  DATA  OF  BIOLOGY. 

substance  which,  in  each  of  the  cells  generating  it,  is  con- 
tained in  a  plexus  of  protoplasmic  threads:  again  a  nitro- 
genous body  diffused  through  a  mass  which  is  now  formed 
out  of  sugar  and  is  now  dissolved  again  into  sugar.  For  it 
appears  that  this  soluble  form  of  carbo-hydrate,  taken  into  the 
liver  from  the  intestine,  is  there,  when  not  immediately 
needed,  stored  up  in  the  form  of  glycogen,  ready  to  be  re-dis- 
solved and  carried  into  the  system  either  for  immediate  use 
or  for  re-deposit  as  glycogen  at  the  places  where  it  is  pre- 
sently to  be  consumed:  the  great  deposit  in  the  liver  and 
the  minor  deposits  in  the  muscles  being,  to  use  the  simile  of 
Prof.  Michael  Foster,  analogous  in  their  functions  to  a  central 
bank  and  branch  banks. 

An  instructive  parallelism  may  be  noted  between  these 
processes  carried  on  in  the  animal  organism  and  those  car- 
ried on  in  the  vegetal  organism.  For  the  carbo-hydrates 
named,  easily  made  to  assume  the  soluble  or  the  insoluble 
form  by  the  addition  or  subtraction  of  a  molecule  of  water, 
and  thus  fitted  sometimes  for  distribution  and  sometimes  for 
accumulation,  are  similarly  dealt  with  in  the  two  cases.  As 
the  animal-starch,  glycogen,  is  now  stored  up  in  the  liver  or 
elsewhere  and  now  changed  into  glucose  to  be  transferred, 
perhaps  for  consumption  and  perhaps  for  re-deposit;  so  the 
vegetal  starch,  made  to  alternate  between  soluble  and  in- 
soluble states,  is  now  carried  to  growing  parts  where  by 
metabolic  change  it  becomes  cellulose  or  other  component  of 
tissue  and  now  carried  to  some  place  where,  changed  back 
into  starch,  it  is  laid  aside  for  future  use;  as  it  is  in  the 
turgid  inside  leaves  of  a  cabbage,  the  root  of  a  turnip,  or  the 
swollen  underground  stem  we  know  as  a  potato :  the  matter 
which  in  the  animal  is  used  up  in  generating  movement  and 
heat,  being  in  the  plant  used  up  in  generating  structures.  Nor 
is  the  parallelism  even  now  exhausted;  for,  as  by  a  plant 
starch  is  stored  up  in  each  seed  for  the  subsequent  use  of  the 
embyro,  so  in  an  embryo-animal  glycogen  is  stored  up  in  the 


METABOLISM.  71 

developing  muscles  for  subsequent  use  in  the  completion  of 
their  structures. 

§  23e.  We  come  now  to  the  supreme  and  all-pervading 
metabolism  which  has  for  its  effects  the  conspicuous  manifes- 
tations of  life — the  nervous  and  muscular  activities.  Here 
comes  up  afresh  a  question  discussed  in  the  edition  of  1861 
— a  question  to  be  reconsidered  in  the  light  of  recent  knowl- 
edge— the  question  what  particular  metabolic  changes  are 
they  by  which  in  muscle  the  energy  existing  under  the  form 
of  molecular  motion  is  transformed  into  the  energy  mani- 
fested as  molar  motion? 

There  are  two  views  respecting  the  nature  of  this  trans- 
formation. One  is  that  the  carbo-hydrate  present  in  muscle 
must,  by  further  metabolism,  be  raised  into  the  form  of  a 
nitrogenous  compound  or  compounds  before  it  can  be  made 
to  undergo  that  sudden  decomposition  which  initiates  mus- 
cular contraction.  The  other  is  the  view  set  forth  in  §  15, 
and  there  reinforced  by  further  illustrations  which  have 
occurred  to  me  while  preparing  this  revised  edition — the 
view  that  the  carbo-hydrate  in  muscle,  everywhere  in  contact 
with  unstable  nitrogenous  substance,  is,  by  the  shock  of  a 
small  molecular  change  in  this,  made  to  undergo  an  extensive 
molecular  change,  resulting  in  the  oxidation  of  its  carbon 
and  consequent  liberation  of  much  molecular  motion.  Both 
of  these  are  at  present  only  hypotheses,  in  support  of  which 
respectively  the  probabilities  have  to  be  weighed.  Let  us 
compare  them  and  observe  on  which  side  the  evidence  prepon- 
derates. 

We  are  obliged  to  conclude  that  in  carnivorous  animals  the 
katabolic  process  is  congruous  with  the  first  of  these  views, 
in  so  far  that  the  evolution  of  energy  must  in  some  way 
result  solely  from  the  fall  of  complex  nitrogenous  compounds 
into  those  simpler  matters  which  make  their  appearance 
as  waste;  for,  practically,  the  carnivorous  animal  has  no 
carbo-hydrates  out  of  which  otherwise  to  evolve  force.  To 


Y2  THE  DATA  OF  BIOLOGY. 

this  admission,  however,  it  should  be  added  that  possibly 
out  of  the  exclusively  nitrogenous  food,  glycogen  or  sugar 
has  to  be  obtained  by  partial  decomposition  before  muscular 
action  can  take  place.  But  when  we  pass  to  animals  having 
food  consisting  mainly  of  carbo-hydrates,  several  difficulties 
stand  in  the  way  of  the  hypothesis  that,  by  further  com- 
pounding, proteids  must  be  formed  from  the  carbo-hydrates 
before  muscular  energy  can  be  evolved.  In  the  first  place 
the  anabolic  change  through  which,  by  the  addition  of  nitro- 
gen, &c.,  a  proteid  is  formed  from  a  carbo-hydrate,  must 
absorb  an  energy  equal  to  a  moiety  of  that  which  is  given 
out  in  the  subsequent  katabolic  change.  There  can  be  no 
dynamic  profit  on  such  part  of  the  transaction  as  effects  the 
composition  and  subsequent  decomposition  of  the  proteid, 
but  only  on  such  part  of  the  transaction  as  effects  the  decom- 
position of  the  carbo-hydrate.  In  the  second  place  there 
arises  the  question — whence  comes  the  nitrogen  required  for 
the  compounding  of  the  carbo-hydrates  into  proteids  ?  There 
is  none  save  that  contained  in  the  serum-albumen  or  other 
proteid  which  the  blood  brings ;  and  there  can  be  no  gain  in 
robbing  this  proteid  of  nitrogen  for  the  purpose  of  forming 
another  proteid.  Hence  the  nitrogenizing  of  the  surplus 
carbo-hydrates  is  not  accounted  for.  One  more  difficulty 
remains.  If  the  energy  given  out  by  a  muscle  results  from 
the  katabolic  consumption  of  its  proteids,  then  the  quantity 
of  nitrogenous  waste  matters  formed  should  be  proportionate 
to  the  quantity  of  work  done.  But  experiments  have  proved 
that  this  is  not  the  case.  Long  ago  it  was  shown  that  the 
amount  of  urea  excreted  does  not  increase  in  anything  like 
proportion  to  the  amount  of  muscular  energy  expended ;  and 
recently  this  has  been  again  shown. 

On  this  statement  a  criticism  has  been  made  to  the  follow- 
ing effect: — Considering  that  muscle  will  contract  when 
deprived  of  oxygen  and  blood  and  must  therefore  contain 
matter  from  which  the  energy  is  derived;  and  considering 
that  since  carbonic  acid  is  given  out  the  required  carbon  and 


METABOLISM.  73 

oxygon  must  be  derived  from  some  component  of  muscle; 
it  results  that  the  energy  must  be  obtained  by  decomposi- 
tion of  a  nitrogenous  body.  To  this  reasoning  it  may  be 
objected,  in  the  first  place,  that  the  conditions  specified  are 
abnormal,  and  that  it  is  dangerous  to  assume  that  what 
takes  place  under  abnormal  conditions  takes  place  also  under 
normal  ones.  In  presence  of  blood  and  oxygen  the  process 
may  possibly,  or  even  probably,  be  unlike  that  which  arises  in 
their  absence :  the  muscular  substance  may  begin  consuming 
itself  when  it  has  not  the  usual  materials  to  consume.  Then, 
in  the  second  place,  and  chiefly,  it  may  be  replied  that  the 
difficulty  raised  in  the  foregoing  argument  is  not  escaped 
but  merely  obscured.  If,  as  is  alleged,  the  carbon  and 
oxygen  from  which  carbonic  acid  is  produced,  form,  under 
the  conditions  stated,  parts  of  a  complex  nitrogenous  sub- 
stance contained  in  muscle,  then  the  abstraction  of  the 
carbon  and  oxygen  must  cause  decomposition  of  this  nitro- 
genous substance;  and  in  that  case  the  excretion  of  nitro- 
genous waste  must  be  proportionate  to  the  amount  of  work 
done,  which  it  is  not.  This  difficulty  is  evaded  by  supposing 
that  the  "  stored  complex  explosive  substance  must  be,  in 
living  muscle,  of  such  nature  "  that  after  explosion  it  leaves 
a  "  nitrogenous  residue  available  for  re-combination  with 
fresh  portions  of  carbon  and  oxygen  derived  from  the  blood 
and  thereby  the  re-constitution  of  the  explosive  substance." 
This  implies  that  a  molecule  of  the  explosive  substance  con- 
sists of  a  complex  nitrogenous  molecule  united  with  a 
molecule  of  carbo-hydrate,  and  that  time  after  time  it  sud- 
denly decomposes  this  carbo-hydrate  molecule  and  thereupon 
takes  up  another  such  from  the  blood.  That  the  carbon  is 
abstracted  from  the  carbo-hydrate  molecule  can  scarcely  be 
said,  since  the  feebler  affinities  of  the  nitrogenous  molecule 
can  hardly  be  supposed  to  overcome  the  stronger  affinities 
of  the  carbo-hydrate  molecule.  The  carbo-hydrate  molecule 
must  therefore  be  incorporated  bodily.  What  is  the  implica- 
tion? The  carbo-hydrate  part  of  the  compound  is  relatively 
stable,  while  the  nitrogenous  part  is  relatively  unstable. 


74  THE  DATA  OF  BIOLOGY. 

Hence  the  hypothesis  implies  that,  time  after  time,  the  un- 
stable nitrogenous  part  overthrows  the  stable  carbo-hydrate 
part,  without  being  itself  overthrown.  This  conclusion,  to 
say  the  least  of  it,  does  not  appear  very  probable. 

The  alternative  hypothesis,  indirectly  supported  as  we  saw 
by  proofs  that  outside  the  body  small  amounts  of  change  in 
nitrogenous  compounds  initiate  large  amounts  of  change 
in  carbonaceous  compounds,  may  in  the  first  place  be  here 
supported  by  some  further  indirect  evidences  of  kindred 
natures.  A  haystack  prematurely  put  together  supplies  one. 
Enough  water  having  been  left  in  the  hay  to  permit  chemical 
action,  the  decomposing  proteids  forming  the  dead  proto- 
plasm in  each  cell,  set  up  decomposition  of  the  carbo-hydrates 
with  accompanying  oxidation  of  the  carbon  and  genesis  of 
heat ;  even  to  the  extent  of  producing  fire.  Again,  as  shown 
above,  this  relation  between  these  two  classes  of  compounds 
is  exemplified  in  the  alimentary  canal;  where,  alike  in  the 
saliva  and  in  the  pancreatic  secretion,  minute  quantities  of 
unstable  nitrogenous  bodies  transform  great  quantities  of 
stable  carbo-hydrates.  Thus  we  find  indirect  reinforcements 
of  the  belief  that  the  katabolic  change  generating  muscular 
energy  is  one  in  which  a  large  decomposition  of  a  carbo- 
hydrate is  set  up  by  a  small  decomposition  of  a  proteid.* 

§  23 f.  A  certain  general  trait  of  animal  organization  may 
fitly  be  named  because  its  relevance,  though  still  more  in- 
direct, is  very  significant.  Under  one  of  its  Aspects  an 
animal  is  an  apparatus  for  the  multiplication  of  energies — a 
set  of  appliances  by  means  of  which  a  minute  amount  of 
motion  initiates  a  larger  amount  of  motion,  and  this  again  a 
still  larger  amount.  There  are  structures  which  do  this 
mechanically  and  others  which  do  it  chemically. 

*  This  interpretation  is  said  to  be  disproved  by  the  fact  that  the  carbo- 
hydrate contained  in  muscle  amounts  to  only  about  1.5  of  the  total  solids.  I 
do  not  see  how  this  statement  is  to  be  reconciled  with  the  statement  ciic*l 
three  pages  back  from  Professor  Michael  Foster,  that  the  deposits  of  gl  -co- 
gen  contained  in  the  liver  and  in  the  muscles  may  be  compared  to  the  deposits 
in  a  central  bank  and  branch  banks. 


METABOLISM.  75 

Associated  with  the  peripheral  ends  of  the  nerves  of  touch 
are  certain  small  bodies — corpuscula  tactus — each  of  which, 
when  disturbed  by  something  in  contact  with  the  skin, 
presses  on  the  adjacent  fibre  more  strongly  than  soft  tissue 
would  do,  and  thus  multiplies  the  force  producing  sensation. 
While  serving  the  further  purpose  of  touching  at  a  distance, 
the  vibrisscB  or  whiskers  of  a  feline  animal  achieve  a  like  end 
in  a  more  effectual  way.  The  external  portion  of  each 
bristle  acts  as  the  long  arm  of  a  lever,  and  the  internal  por- 
tion as  the  short  arm.  The  result  is  that  a  slight  touch  at 
the  outer  end  of  the  bristle  produces  a  considerable  pressure 
of  the  inner  end  on  the  nerve-terminal :  so  intensifying  the 
impression.  In  the  hearing  organs  of  various  inferior  types 
of  animals,  the  otolites  in  contact  with  the  auditory  nerves, 
when  they  are  struck  by  sound-waves,  give  to  the  nerves 
much  stronger  impressions  than  these  would  have  were  they 
simply  immersed  in  loose  tissue;  and  in  the  ears  of  de- 
veloped creatures  there  exist  more  elaborate  appliances  for 
augmenting  the  effects  of  aerial  vibrations.  From  this  mul- 
tiplication of  molar  actions  let  us  pass  to  the  multiplication 
of  molecular  actions.  The  retina  is  made  up  of  minute  rods 
and  cones,  so  packed  together  side  by  side  that  they  can  be 
separately  affected  by  the  separate  parts  of  the  images  of 
objects.  As  each  of  them  is  but  TTr.tanrth  of  an  inch  in 
diameter,  the  ethereal  undulations  falling  upon  it  can  pro- 
duce an  amount  of  change  almost  infinitesimal — an  amount 
probably  incapable  of  exciting  a  nerve-centre,  or  indeed  of 
overcoming  the  molecular  inertia  of  the  nerve  leading  to  it. 
But  in  close  proximity  are  layers  of  granules  into  which  the 
rods  and  cones  send  fibres,  and  beyond  these,  about  yiirth 
of  an  inch  from  the  retinal  layer,  lie  ganglion-cells,  in 
each  of  which  a  minute  disturbance  may  readily  evolve  a 
larger  disturbance;  so  that  by  multiplication,  single  or  per- 
haps double,  there  is  produced  a  force  sufficient  to  excite 
the  fibre  connected  with  the  centre  of  vision.  Such,  at  least, 
judging  from  the  requirement  and  the  structure,  seems  to  me 


76  THE  DATA  OF  BIOLOGY. 

the  probable  interpretation  of  the  visual  process;  though 
whether  it  is  the  accepted  one  I  do  not  know. 

But  now,  carrying  with  us  the  conception  made  clear  by 
the  first  cases  and  suggested  by  the  last,  we  shall  appreciate 
the  extent  to  which  this  general  physiological  method,  as  we 
may  call  it,  is  employed.  The  convulsive  action  caused  by 
tickling  shows  it  conspicuously.  An  extremely  small  amount 
of  molecular  change  in  the  nerve-endings  produces  an  im- 
mense amount  of  molecular  change,  and  resulting  molar 
motion,  in  the  muscles.  Especially  is  this  seen  in  one  whose 
spinal  cord  has  been  so  injured  that  it  no  longer  conveys 
sensations  from  the  lower  limbs  to  the  brain;  and  in  whom, 
nevertheless,  tickling  of  the  feet  produces  convulsive  actions 
of  the  legs  more  violent  even  than  result  when  sensation 
exists:  clearly  proving  that  since  the  minute  molecular 
change  produced  by  the  tickling  in  the  nerve-terminals  can- 
not be  equivalent  in  quantity  to  the  amount  implied  by 
the  muscular  contraction,  there  must  be  a  multiplication  of 
it  in  those  parts  of  the  spinal  cord  whence  issue  the  reflex 
stimuli  to  the  muscles. 

Keturning  now  to  the  question  of  metabolism,  we  may  see 
that  the  processes  of  multiplication  above  supposed  to  take 
place  in  muscle,  are  analogous  in  their  general  nature  to 
various  other  physiological  processes.  Carrying  somewhat 
further  the  simile  used  in  §  15  and  going  back  to  the  days 
when  detonators,  though  used  for  small  arms,  were  not  used 
for  artillery,  we  may  compare  the  metabolic  process  in 
muscle  to  that  which  would  take  place  if  a  pistol  were  fired 
against  the  touch-hole  of  a  loaded  cannon :  the  cap  exploding 
the  pistol  and  the  pistol  the  cannon.  For  in  the  case  of  the 
muscle,  the  implication  is  that  a  nervous  discharge  works  in 
certain  unstable  proteids  through  which  the  nerve-endings 
are  distributed,  a  small  amount  of  molecular  change;  that 
the  shock  of  this  causes  a  much  larger  amount  of  molecular 
change  in  the  inter-diffused  carbo-hydrate,  with  accompanying 
oxidation  of  its  carbon ;  and  that  the  heat  liberated  sets  up  a 
transformation,  probably  isomeric,  in  the  contractile  substance 


METABOLISM.  77 

of  the  muscular  fibre :  an  interpretation  supported  by  cases  in 
which  small  rises  and  falls  of  temperature  cause  alternating 
isomeric  changes ;  as  instance  Mensel's  salt. 

Ending  here  this  exposition,  somewhat  too  speculative  and 
running  into  details  inappropriate  to  a  work  of  this  kind,  it 
suffices  to  note  the  most  general  facts  concerning  metabolism. 
Regarded  as  a  whole  it  includes,  in  the  first  place,  those 
anabolic  or  building-up  processes  specially  characterizing 
plants,  during  which  the  impacts  of  ethereal  undulations  are 
stored  up  in  compound  molecules  of  unstable  kinds;  and  it 
includes,  in  the  second  place,  those  katabolic  or  tumbling- 
down  changes  specially  characterizing  animals,  during  which 
this  accumulated  molecular  motion  (contained  in  the  food 
directly  or  indirectly  supplied  by  plants),  is  in  large  measure 
changed  into  those  molar  motions  constituting  animal  activi- 
ties. There  are  multitudinous  metabolic  changes  of  minor 
kinds  which  are  ancillary  to  these — many  katabolic  changes 
in  plants  and  many  anabolic  changes  in  animals — but  these 
are  the  essential  ones.* 

*  Before  leaving  the  topic  let  me  remark  that  the  doctrine  of  metabolism 
is  at  present  in  its  inchoate  stage,  and  that  the  prevailing  conclusions  should 
be  held  tentatively.  As  showing  this  need  an  anomalous  fact  may  be  named. 
It  was  long  held  that  gelatine  is  of  small  value  as  food,  and  though  it  is  now 
recognized  as  valuable  because  serving  the  same  purposes  as  fats  and  carbo- 
hydrates, it  is  still  held  to  be  valueless  for  structural  purposes  (save  for  some 
inactive  tissue) ;  and  this  estimate  agrees  with  the  fact  that  it  is  a  relatively 
stable  nitrogenous  compound,  and  therefore  unfit  for  those  functions  per- 
formed by  unstable  nitrogenous  compounds  in  the  muscular  and  other  tissues. 
But  if  this  is  true,  it  seems  a  necessary  implication  that  such  substances  as 
hair,  wool,  feathers,  and  all  dermal  growths  chemically  akin  to  gelatine,  and 
even  more  stable,  ought  to  be  equally  innutritive  or  more  innutritive.  In  that 
case,  however,  what  are  we  to  say  of  the  larva  of  the  clothes-moth,  which 
subsists  exclusively  on  one  or  other  of  these  substances,  and  out  of  it  forms 
all  those  unstable  nitrogenous  compounds  needful  for  carrying  on  its  life 
and  developing  its  tissues  ?  Or  again,  how  are  we  to  understand  the  nutri- 
tion of  the  book-worm,  which,  in  the  time-stained  leaves  through  which  it 
burrows,  finds  no  proteid  save  that  contained  in  the  dried-up  size,  which  is  a 
form  of  gelatine;  or,  once  more,  in  what  form  is  the  requisite  amount  of 
nitrogenous  substance  obtained  by  the  coleopterous  larva  which  eats  holes  in 
wood  a  century  old  ? 


CHAPTER  IV.* 

PROXIMATE     CONCEPTION    OF    LIFE. 

§  24.  To  those  who  accept  the  general  doctrine  of  Evolu- 
tion, it  need  scarcely  be  pointed  out  that  classifications  are 
subjective  conceptions,  which  have  no  absolute  demarcations 
in  Nature  corresponding  to  them.  They  are  appliances  by 
which  we  limit  and  arrange  the  matters  under  investigation ; 
and  so  facilitate  our  thinking.  Consequently,  when  we  at- 
tempt to  define  anything  complex,  or  make  a  generalization 
of  facts  other  than  the  most  simple,  we  can  scarcely  ever 
avoid  including  more  than  we  intended,  or  leaving  out  some- 
thing which  should  be  taken  in.  Thus  it  happens  that  on 
seeking  a  definite  idea  of  Life,  we  have  great  difficulty  in 
finding  one  that  is  neither  more  nor  less  than  sufficient.  Let 
us  look  at  a  few  of  the  most  tenable  definitions  that  have 
been  given.  While  recognizing  the  respects  in  which  they 
are  defective,  we  shall  see  what  requirements  a  more  satis- 
factory one  must  fulfil. 

Schelling  said  that  Life  is  the  tendency  to  individuation. 
This  formula,  until  studied,  conveys  little  meaning.  But  we 
need  only  consider  it  as  illustrated  by  the  facts  of  develop- 
ment, or  by  the  contrast  between  lower  and  higher  forms  of 

*  This  chapter  and  the  following  two  chapters  originally  appeared  in 
Tart  III  of  the  original  edition  of  the  Principles  of  Psychology  (1855):  form- 
ing a  preliminary  which,  though  indispensable  to  the  argument  there  devel- 
oped, was  somewhat  parenthetical.  Having  now  to  deal  with  the  general 
science  of  Biology  before  the  more  special  one  of  Psychology,  it  becomes 
possible  to  transfer  these  chapters  to  their  proper  place. 
78 


PROXIMATE  CONCEPTION  OF  LIFE.  79 

life,  to  recognize  its  significance;  especially  in  respect  of 
comprehensiveness.  As  before  shown,  however  (First  Prin- 
ciples, §  56),  it  is  objectionable;  partly  on  the  ground  that  it 
refers  not  so  much  to  the  functional  changes  constituting 
Life,  as  to  the  structural  changes  of  those  aggregates  of 
matter  which  manifest  Life;  and  partly  on  the  ground  that 
it  includes  under  the  idea  Life,  much  that  we  usually  exclude 
from  it :  for  instance — crystallization. 

The  definition  of  Richerandj — "  Life  is  a  collection  of 
phenomena  which  succeed  each  other  during  a  limited  time 
in  an  organized  body," — is  liable  to  'the  fatal  criticism,  that 
it  equally  applies  to  the  decay  which  goes  on  after  death. 
For  this,  too,  is  "  a  collection  of  phenomena  whiclr  succeed 
each  other  during  a  limited  time  in  an  organized  body." 

"  Life,"  according  to  De  Blainville,  "  is  the  two-fold 
internal  movement  of  composition  and  decomposition,  at  once 
general  and  continuous."  This  conception  is  in  some  re- 
spects too  narrow,  and  in  other  respects  too  wide.  On  the 
one  hand,  while  it  expresses  what  physiologists  distinguish 
as  vegetative  life,  it  does  not  indicate  those  nervous  and 
muscular  functions  which  form  the  most  conspicuous  and 
distinctive  classes  of  vital  phenomena.  On  the  other  hand, 
it  describes  not  only  the  integrating  and  disintegrating  pro- 
cess going  on  in  a  living  body,  but  it  equally  well  describes 
those  going  on  in  a  galvanic  battery;  which  also  exhibits  a 
"  two-fold  internal  movement  of  composition  and  decomposi- 
tion, at  once  general  and  continuous." 

Elsewhere,  I  have  myself  proposed  to  define  Life  as  "  the 
co-ordination  of  actions."  *  This  definition  has  some  advan- 
tages. It  includes  all  organic  changes,  alike  of  the  viscera, 
the  limbs,  and  the  brain.  It  excludes  the  great  mass  of 
inorganic  changes;  which  display  little  or  no  co-ordination. 
By  making  co-ordination  the  specific  character  of  vitality,  it 
involves  the  truths,  that  an  arrest  of  co-ordination  is  death, 

*  See  Westminster  Review  for  April,  1852.— Art.  IV.  "A  Theory  of 
Population."  See  Appendix  A. 


gO  THE  DATA  OF  BIOLOGY. 

and  that  imperfect  co-ordination  is  disease.  Moreover,  it 
harmonizes  with  our  ordinary  ideas  of  life  in  its  different 
grades;  seeing  that  the  organisms  which  we  rank  as  low  in 
iheijr  degrees  of  life,  are  those  which  display  but  little  co- 
ordination of  actions ;  and  seeing  that  from  these  up  to  man, 
the  recognized  increase  in  degree  of  life  corresponds  with  an 
increase  jn  the  extent  and  complexity  of  co-ordinations.  But, 
like  the  others,  this  definition  includes  too  much.  It  may 
be  said  of  the  Solar  System,  with  its  regularly-recurring 
movements  and  its  self-balancing  perturbations,  that  it,  also, 
exhibits  co-ordination  of  actions.  And  however  plausibly  it 
may  be  argued  that,  in  the  abstract,  the  motions  of  the 
planets  and  satellites  are  as  properly  comprehended  in  the 
idea  of  life  as  the  changes  going  on  in  a  motionless,  unsensi- 
tive  seed:  yet,  it  must  be  admitted  that  they  are  foreign  to 
that  idea  as  commonly  received,  and  as  here  to  be  formulated. 

It  remains  to  add  the  definition  since  suggested  by  Mr. 
G.  H.  Lewes — "  Life  is  a  series  of  definite  and  successive 
changes,  both  of  structure  and  composition,  which  take  place 
within  an  individual  without  destroying  its  identity."  The 
last  fact  which  this  statement  brings  into  view — the  persis- 
tence of  a  living  organism  as  a  whole,  in  spite  of  the  con- 
tinuous removal  and  replacement  of  its  parts — is  important. 
But  otherwise  it  may  be  argued  that,  since  changes  of  struc- 
ture and  composition,  though  concomitants  of  muscular  and 
nervous  actions,  are  not  the  muscular  and  nervous  actions 
themselves,  the  definite  excludes  the  more  visible  move- 
ments with  which  our  idea  of  life  is  most  associated;  and 
further  that,  in  describing  vital  changes  as  a  series,  it  scarcely 
includes  the  fact  that  many  of  them,  as  Nutrition,  Circula- 
tion, Respiration,  and  Secretion,  in  their  many  subdivisions, 
go  on  simultaneously. 

Thus,  however  well  each  of  these  definitions  expresses  the 
phenomena  of  life  under  some  of  its  aspects,  no  one  of  them 
is  more  than  approximately  true.  It  may  turn  out  that  to 
find  a  formula  which  will  bear  every  test  is  impossible. 


PROXIMATE   CONCEPTION  OP  LIFE.  81 

Meanwhile,  it  is  possible  to  frame  a  more  adequate  formula 
than  any  of  the  foregoing.  As  we  shall  presently  find,  these 
all  omit  an  essential  peculiarity  of  vital  changes  in  general — 
a  peculiarity  which,  perhaps  more  than  any  other,  distin- 
guishes them  from  non-vital  changes.  Before  specifying  this 
peculiarity,  however,  it  will  be  well  to  trace  our  way,  step 
by  step,  to  as  complete  an  idea  of  Life  as  may  be  reached 
from  our  present  stand-point;  by  doing  which  we  shall  both 
see  the  necessity  for  each  limitation  as  it  is  made,  and  ulti- 
mately be  led  to  feel  the  need  for  a  further  limitation. 

And  here,  as  the  best  mode  of  determining  what  are  the 
traits  which  distinguish  vitality  from  non-vitality,  we  shall 
do  well  to  compare  the  two  most  unlike  kinds  of  vitality,  and 
see  in  what  they  agree.  Manifestly,  that  which  is  essential 
to  Life  must  be  that  which  is  common  to  Life  of  all  orders. 
And  manifestly,  that  which  is  common  to  all  forms  of  Life, 
will  most  readily  be  seen  on  contrasting  those  forms  of  Life 
which  have  the  least  in  common,  or  are  the  most  unlike.* 

i 

§  25.  Choosing  assimilation,  then,  for  our  example  of 
bodily  life,  and  reasoning  for  our  example  of  that  life  known 
as  intelligence;  it  is  first  to  be  observed,  that  they  are  both 
processes  of  change.  Without  change,  food  cannot  be  taken 
into  the  blood  nor  transformed  into  tissue;  without  change, 
there  can  be  no  getting  from  premisses  to  conclusion.  And 
it  is  this  conspicuous  display  of  changes  which  forms  the 
substratum  of  our  idea  of  Life  in  general.  Doubtless  we  see 
innumerable  changes  to  which  no  notion  of  vitality  attaches. 
Inorganic  bodies  are  ever  undergoing  changes  of  temperature, 
changes  of  colour,  changes  of  aggregation;  and  decaying 
organic  bodies  also.  But  it  will  be  admitted  that  the  great 

*  This  paragraph  replaces  a  sentence  that,  in  The  Principles  of  Psy- 
chology, referred  to  a  preceding  chapter  on  "  Method ; "  in  which  the  mode  of 
procedure  here  indicated  was  set  forth  as  a  mode  to  be  systematically 
pursued  in  the  choice  of  hypotheses.  This  chapter  on  Method  is  now 
included,  along  with  other  matter,  in  a  volume  entitled  Various  Frag- 
ment*. 


82  THE   DATA   OP  BIOLOGY. 

majority  of  the  phenomena  displayed  by  inanimate  bodies, 
are  statical  and  not  dynamical;  that  the  modifications  of 
inanimate  bodies  are  mostly  slow  and  unobtrusive;  that  on 
the  one  hand,  when  we  see  sudden  movements  in  inanimate 
bodies,  we  are  apt  to  assume  living  agency,  and  on  the  other 
hand,-  when  we  see  no  movements  in  living  bodies,  we  are 
apt  to  assume  death.  Manifestly  then,  be  the  requisite  quali- 
fications what  they  may,  a  true  idea  of  Life  must  be  an  idea 
of  some  kind  of  change  or  changes. 

On  .further  comparing  assimilation  and  reasoning,  with  a 
view  of  seeing  in  what  respect  the  changes  displayed  in  both 
differs  from  non-vital  changes,  we  find  that  they  differ  in 
being  not  simple  changes;  in  each  case  there  are  successive 
changes.  The  transformation  of  food  into  tissue  involves 
mastication,  deglutition,  chymification,  chylification,  absorp- 
tion, and  those  various  actions  gone  through  after  the  lacteal 
ducts  have  poured  their  contents  into  the  blood.  Carrying  on 
an  argument  necessitates  a  long  chain  of  states  of  conscious- 
ness; each  implying  a  change  of  the  preceding  state.  Inor- 
ganic changes,  however,  do  not  in  any  considerable  degree 
exhibit  this  peculiarity.  It  is  true  that  from  meteorologic 
causes,  inanimate  objects  are  daily,  sometimes  hourly,  under- 
going modifications  of  temperature,  of  bulk,  of  hygrometric 
and  electric  condition.  Not  only,  however,  do  these  modifica- 
tions lack  that  conspicuousness  and  that  rapidity  of  succession 
which  vital  ones  possess,  but  vital  ones  form  an  additional 
series.  Living  as  well  as  not-living  bodies  are  affected 
by  atmospheric  influences;  and  beyond  the  changes  which 
these  produce,  living  bodies  exhibit  other  changes,  more 
numerous  and  more  marked.  So  that  though  organic  change 
is  not  rigorously  distinguished  from  inorganic  change  by 
presenting  successive  phases;  yet  vital  change  so  greatly 
exceeds  other  change  in  this  respect,  that  we  may  consider 
it  as  a  distinctive  character.  Life,  then,  as  thus  roughly 
differentiated,  may  be  regarded  as  change  presenting  succes- 
sive phases;  or  otherwise,  as  a  series  of  changes.  And  it 


PROXIMATE  CONCEPTION  OF  LIFE.  83 

should  be  observed,  as  a  fact  in  harmony  with  this  conception, 
that  the  higher  the  life  the  more  conspicuous  the  variations. 
On  comparing  inferior  with  superior  organisms,  these  last  will 
be  seen  to  display  more  rapid  changes,  or  a  more  lengthened 
series  of  them,  or  both. 

On  contemplating  afresh  our  two  typical  phenomena,  we 
may  see  that  vital  change  is  further  distinguished  from  non- 
vital  change,  by  being  made  up  of  many  simultaneous  changes. 
Nutrition  is  not  simply  a  series  of  actions,  but  includes  many 
actions  going  on  together.  During  mastication  the  stomach 
is  busy  with  food  already  swallowed,  on  which  it  is  pouring 
out  solvent  fluids  and  expending  muscular  efforts.  While  the 
stomach  is  still  active,  the  intestines  are  performing  their 
secretive,  contractile,  and  absorbent  functions;  and  at  the 
same'  time  that  one  meal  is  being  digested,  the  nutriment 
obtained  from  a  previous  meal  is  undergoing  transformation 
into  tissue.  So  too  is  it,  in  a  certain  sense,  with  mental 
changes.  Though  the  states  of  consciousness  which  make 
up  an  argument  occur  in  series,  yet,  as  each  of  them  is  com- 
plex, a  number  of  simultaneous  changes  have  taken  place  in 
establishing  it.  Here  as  before,  however,  it  must  be 

admitted  that  the  distinction  between  animate  and  inanimate 
is  not  precise.  No  mass  of  dead  matter  can  have  its  tem- 
perature altered,  without  at  the  same  time  undergoing  an 
alteration  in  bulk,  and  sometimes  also  in  hygrometric  state. 
An  inorganic  body  cannot  be  compressed,  without  being  at 
the  same  time  changed  in  form,  atomic  arrangement,  tem- 
perature, and  electric  condition.  And  in  a  vast  and  mobile 
aggregate  like  the  sea,  the  simultaneous  as  well  as  the  succes- 
sive changes  outnumber  those  going  on  in  an  animal. 
Nevertheless,  speaking  generally,  a  living  thing  is  distin- 
guished from  a  dead  thing  by  the  multiplicity  of  the  changes 
at  any  moment  taking  place  in  it.  Moreover,  by  this  pecu- 
liarity, as  by  the  previous  one,  not  only  is  the  vital  more  or 
less  clearly  marked  off  from  the  non-vital;  but  creatures 
possessing  high  vitality  are  marked  off  from  those  possessing 


g4  THE  DATA  OP  BIOLOGY. 

low  vitality.  It  needs  but  to  contrast  the  many  organs  co- 
operating in  a  mammal,  with  the  few  in  a  polype,  to  see  that 
the  actions  which  are  progressing  together  in  the  body  of  the 
first,  as  much  exceed  in  number  the  actions  progressing  to- 
gether in  the  body  of  the  last,  as  these  do  those  in  a  stone.  As 
at  present  conceived,  then,  Life  consists  of  simultaneous  and 
successive  changes. 

Continuance  of  the  comparison  shows  that  vital  changes, 
both  visceral  and  cerebral,  differ  from  other  changes  in  their 
heterogeneity.  Neither  the  simultaneous  acts  nor  the  serial 
acts,  which  together  constitute  the  process  of  digestion,  are 
alike.  The  states  of  consciousness  comprised  in  any  ratio- 
cination are  not  repetitions  one  of  another,  either  in  com- 
position or  in  modes  of  dependence.  Inorganic  processes,  on 
the  other  hand,  even  when  like  organic  ones  in  the  number 
of  the  simultaneous  and  successive  changes  they  involve,  are 
unlike  them  in  the  relative  homogeneity  of  these  changes. 
In  the  case  of  the  sea,  just  referred  to,  it  is  observable  that 
countless  as  are  the  actions  at  any  moment  going  on,  they  are 
mostly  mechanical  actions  that  are  to  a  great  degree  similar; 
and  in  this  respect  differ  widely  from  the  actions  at  any 
moment  taking  place  in  an  organism.  Even  where  life  is 
nearly  simulated,  as  by  the  working  of  a  steam-engine,  we 
see  that  considerable  as  is  the  number  of  simultaneous 
changes,  and  rapid  as  are  the  successive  ones,  the  regularity 
with  which  they  soon  recur  in  the  same  order  and  degree, 
renders  them  unlike  those  varied  changes  exhibited  by  a 
living  creature.  Still,  this  peculiarity,  like  the  fore- 

going ones,  does  not  divide  the  two  classes  of  changes  with 
precision;  since  there  are  inanimate  things  presenting  con- 
siderable heterogeneity  of  change:  for  instance,  a  cloud. 
The  variations  of  state  which  this  undergoes,  both  simulta- 
neous and  successive,  are  many  and  quick;  and  they  differ 
widely  from  one  another  both  in  quality  and  quantity.  At 
the  same  instant  there  may  occur  change  of  position,  change 
of  form,  change  of  size,  change  of  density,  change  of  colour, 


/*• 

PROXIMATE  CONCEPTION  OF  LIFE.  85 

change  of  temperature,  change  of  electric  state;  and  these 
several  kinds  of  change  are  continuously  displayed  in  different 
degrees  and  combinations.  Yet  when  we  observe  that  very 
few  inorganic,  objects  manifest  heterogeneity  of  change  com- 
parable to  that  manifested  by  organic  objects,  and  further, 
that  in  ascending  from  low  to  high  forms  of  life,  we  meet 
with  an  increasing  variety  in  the  kinds  of  changes  displayed ; 
we  see  that  there  is  here  a  further  leading  distinction  between 
vital  and  non-vital  actions.  According  to  this  modified  con- 
ception, then,  Life  is  made  up  of  heterogeneous  changes  both 
simultaneous  and  successive. 

If,  now,  we  look  for  some  trait  common  to  the  nutritive 
and  logical  processes,  by  which  they  are  distinguished  from 
those  inorganic  processes  that  are  most  like  them  in  the 
heterogeneity  of  the  simultaneous  and  successive  changes 
they  comprise,  we  discover  that  they  are  distinguished  by 
the  combination  among  their  constituent  changes.  The  acts 
which  make  up  digestion  are  mutually  dependent.  Those 
composing  a  train  of  reasoning  are  in  close  connection.  And, 
generally,  it  is  to  be  remarked  of  vital  changes,  that 
each  is  made  possible  by  all,  and  all  are  affected  by  each. 
Respiration,  circulation,  absorption,  secretion,  in  their  many 
sub-divisions,  are  bound  up  together.  Muscular  contraction 
involves  chemical  change,  change  of  temperature,  and  change 
in  the  excretions.  Active  thought  influences  the  operations 
of  the  stomach,  of  the  heart,  of  the  kidneys.  But  we  miss 
this  union  among  non-vital  activities.  Life-like  as  may 
seem  the  action  of  a  volcano  in  respect  of  the  heterogeneity 
of  its  many  simultaneous  and  successive  changes,  it  is  not  life- 
like in  respect  of  their  combination.  Though  the  chemical, 
mechanical,  thermal,  and  electric  phenomena  exhibited  have 
some  inter-dependence,  yet  the  emissions  of  stones,  mud,  lava, 
flame,  ashes,  smoke,  steam,  take  place  irregularly  in  quantity, 
order,  intervals,  and  mode  of  conjunction.  Even  here, 

however,  it  cannot  be  said  that  inanimate  things  present  no 
parallels  to  animate  ones.      A  glacier  may  be  instanced  as 
7 


86  THE  DATA  OP   BIOLOGY. 

showing  nearly  as  much  combination  in  its  change  as  a 
plant  of  the  lowest  organization.  It  is  ever  growing  and 
ever  decaying;  and  the  rates  of  its  composition  and  decom- 
position preserve  a  tolerably  constant  ratio.  It  moves;  and 
its  motion  is  in  immediate  dependence  on  its  thawing.  It 
emits  a  torrent  of  water,  which,  in  common  with  its  motion, 
undergoes  annual  variations  as  plants  do.  During  part  of 
the  year  the  surface  melts  and  freezes  alternately;  and  on 
these  changes  depend  the  variations  in  movement,  and  in 
efflux  of  water.  Thus  we  have  growth,  decay,  changes  of 
temperature,  changes  of  consistence,  changes  of  velocity, 
changes  of  excretion,  all  going  on  in  connexion;  and  it  may 
be  as  truly  said  of  a  glacier  as  of  an  animal,  that  by  cease- 
less integration  and  disintegration  it  gradually  undergoes  an 
entire  change  of  substance  without  losing  its  individuality. 
This  exceptional  instance,  however,  will  scarcely  be  held 
to  obscure  that  broad  distinction  from  inorganic  processes 
which  organic  processes  derive  from  the  combination  among 
their  constituent  changes.  And  the  reality  of  this  distinction 
becomes  yet  more  manifest  when  we  find  that,  in  common 
with  previous  ones,  it  not  only  marks  off  the  living  from  the 
not-living,  but  also  things  which  live  little  from  things  which 
live  much.  For  while  the  changes  going  on  in  a  plant  or  a 
zoophyte  are  so  imperfectly  combined  that  they  can  continue 
after  it  has  been  divided  into  two  or  more  pieces,  the  com- 
bination among  the  changes  going  on  in  a  mammal  is  so 
close  that  no  part  cut  off  from  the  rest  can  live,  and  any 
considerable  disturbance  of  one  chief  function  causes  a  cessa- 
tion of  the  others.  Hence,  as  we  now  regard  it,  Life  is  a  com- 
bination of  heterogeneous  changes,  both  simultaneous  and 
successive. 

When  we  once  more  look  for  a  character  common  to  these 
two  kinds  of  vital  action,  we  perceive  that  the  combinations 
of  heterogeneous  changes  which  constitute  them,  differ  from 
the  few  combinations  which  they  otherwise  resemble,  in  re- 


PROXIMATE  CONCEPTION  OF  LIFE.  87 

spect  of  definiteness.  The  associated  changes  going  011  in  a 
glacier,  admit  of  indefinite  variation.  Under  a  conceivable 
alteration  of  climate,  its  thawing  and  its  progression  may  be 
stopped  for  a  million  years,  without  disabling  it  from  again 
displaying  these  phenomena  under  appropriate  conditions. 
By  a  geological  convulsion,  its  motion  may  be  arrested  with- 
out an  arrest  of  its  thawing;  or  by  an  increase  in  the  in- 
clination of  the  surface  it  slides  over,  its  motion  may  be 
accelerated  without  accelerating  its  rate  of  dissolution. 
Other  things  remaining  the  same,  a  more  rapid  deposit  of 
snow  may  cause  great  increase  of  bulk;  or,  conversely,  the 
accretion  may  entirely  cease,  and  yet  all  the  other  actions 
continue  until  the  mass  disappears.  Here,  then,  the  combina- 
tion has  none  of  that  deflniteness  which,  in  a  plant,  marks 
the  mutual  dependence  of  respiration,  assimilation,  and  cir- 
culation; much  less  has  it  that  definiteness  seen  in  the 
mutual  dependence  of  the  chief  animal  functions;  no  one  of 
which  can  be  varied  without  varying  the  rest;  no  one  of 
which  can  go  on  unless  the  rest  go  on.  Moreover,  this 
definiteness  of  combination  distinguishes  the  changes  occur- 
ring in  a  living  body  from  those  occurring  in  a  dead  one. 
Decomposition  exhibits  both  simultaneous  and  successive 
changes,  which  are  to  some  extent  heterogeneous,  and  in  a 
sense  combined;  but  they  are  not  combined  in  a  definite 
manner.  They  vary  according  as  the  surrounding  medium 
is  air,  water,  or  earth.  They  alter  in  nature  with  the  tem- 
perature. If  the  local  conditions  are  unlike,  they  progress 
differently  in  different  parts  of  the  mass,  without  mutual 
influence.  They  may  end  in  producing  gases,  or  adipocire, 
or  the  dry  substance  of  which  mummies  consist.  They  may 
occupy  a  few  days  or  thousands  of  years.  Thus,  neither  in 
their  simultaneous  nor  in  their  successive  changes,  do  dead 
bodies  display  that  definiteness  of  combination  which  charac- 
terizes living  ones.  It  is  true  that  in  some  inferior 
creatures  the  cycle  of  successive  changes  admits  of  a  certain 


88  THE  DATA  OF  BIOLOGY. 

indefinitcness — that  it  may  be  suspended  for  a  long  period 
by  desiccation  or  freezing,  and  may  afterwards  go  on  as 
though  there  had  been  no  breach  in  its  continuity.  But  the 
circumstance  that  only  a  low  order  of  life  can  have  its 
changes  thus  modified,  serves  but  to  suggest  that,  like  the 
previous  characteristics,  this  characteristic  of  definiteness  in 
its  combined  changes,  distinguishes  high  vitality  from  low 
vitality,  as  it  distinguishes  low  vitality  from  inorganic  pro- 
cesses. Hence,  our  formula  as  further  amended  reads  thus: 
— Life  is  a  definite  combination  of  heterogenous  changes, 
both  simultaneous  and  successive. 

Finally,  we  shall  still  better  express  the  facts  if,  instead 
of  saying  a  definite  combination  of  heterogeneous  changes, 
we  say  the  definite  combination  of  heterogeneous  changes. 
As  it  at  present  stands,  the  definition  is  defective  both  in 
allowing  that  there  may  be  other  definite  combinations  of 
heterogeneous  changes,  and  in  directing  attention  to  the 
heterogeneous  changes  rather  than  to  the  definiteness  of  their 
combination.  Just  as  it  is  not  so  much  its  chemical  elements 
which  constitute  an  organism,  as  it  is  the  arrangement  of 
them  into  special  tissues  and  organs ;  so  it  is  not  so  much  its 
heterogeneous  changes  which  constitute  Life,  as  it  is  the  co- 
ordination of  them.  Observe  what  it  is  that  ceases  when  life 
ceases.  In  a  dead  body  there  are  going  on  heterogeneous 
changes,  both  simultaneous  and  successive.  What  then  has 
disappeared?  The  definite  combination  has  disappeared. 
Mark,  too,  that  however  heterogeneous  the  simultaneous  and 
successive  changes  exhibited  by  such  an  inorganic  object  as 
a  volcano,  we  much  less  tend  to  think  of  it  as  living  than  we 
do  a  watch  or  a  steam-engine,  which,  though  displaying 
changes  that,  serially  contemplated,  are  largely  homogeneous, 
displays  them  definitely  combined.  So  dominant  an  element 
is  this  in  our  idea  of  Life,  that  even  when  an  object  is 
motionless,  yet,  if  its  parts  be  definitely  combined,  we  con- 
clude either  that  it  has  had  life,  or  has  been  made  by  some- 
thing having  life.  Thus,  then,  we  conclude  that  Life  is — the 


PROXIMATE  CONCEPTION  OF  LIFE.  89 

definite  combination  of  heterogeneous  changes,  both  simul- 
taneous and  successive. 

§  26.  Such  is  the  conception  at  which  we  arrive  without 
changing  our  stand-point.  It  is,  however,  an  incomplete 
conception.  This  ultimate  formula  (which  is  to  a  consider- 
able extent  identical  with  one  above  given — "  the  co-ordina- 
tion of  actions ;  "  seeing  that  "  definite  combination "  is 
synonymous  with  "co-ordination,"  and  "changes  both 
simultaneous  and  successive  "  are  comprehended  under  the 
term  "  actions ;  "  but  which  differs  from  it  in  specifying  the 
fact,  that  the  actions  or  changes  are  "heterogeneous") — this 
ultimate  formula,  I  say,  is  after  all  but  a  rude  approximation. 
It  is  true  that  it  does  not  fail  by  including  the  growth  of 
a  crystal;  for  the  successive  changes  this  implies  cannot  be 
called  heterogeneous.  It  is  true  that  the  action  of  a  galvanic 
battery  is  not  comprised  in  it;  since  here,  too,  heterogeneity 
is  not  exhibited  by  the  successive  changes.  It  is  true  that  by 
this  same  qualification  the  motions  of  the  Solar  System  are 
excluded,  as  are  also  those  of  a  watch  and  a  steam-engine. 
It  is  true,  moreover,  that  while,  in  virtue  of  their  heteroge- 
neity, the  actions  going  on  in  a  cloud,  in  a  volcano,  in  a 
glacier,  fulfil  the  definition ;  they  fall  short  of  it  in  lacking 
definiteness  of  combination.  It  is  further  true  that  this  de- 
finiteness  of  combination  distinguishes  the  changes  taking 
place  in  an  organism  during  life  from  those  which  commence 
at  death.  And  beyond  all  this  it  is  true  that,  as  well  as 
serving  to  mark  off,  more  or  less  clearly,  organic  actions  from 
inorganic  actions,  each  member  of  the  definition  serves  to 
mark  off  the  actions  constituting  high  vitality  from  those 
constituting  low  vitality;  seeing  that  life  is  high  in  propor- 
tion to  the  number  of  successive  changes  occurring  between 
birth  and  death ;  in  proportion  to  the  number  of  simultaneous 
changes;  in  proportion  to  the  heterogeneity  of  the  changes; 
in  proportion  to  the  combination  subsisting  among  the 
changes;  and  in  proportion  to  the  definiteness  of  their  com- 


90  THE   DATA   OF   BIOLOGY. 

bination.  Nevertheless,  answering  though  it  does  to  so 
many  requirements,  this  definition  is  essentially  defective. 
The  definite  combination  of  heterogeneous  changes,  both 
simultaneous  and  successive,  is  a  formula  which  fails  to  call 
up  an  adequate  conception.  And  it  fails  from  omitting  the 
most  distinctive  peculiarity — the  peculiarity  of  which  we 
have  the  most  familiar  experience,  and  with  which  our  notion 
of  Life  is,  more  than  with  any  other,  associated.  It  remains 
now  to  supplement  the  conception  by  the  addition  of  this 
peculiarity. 


CHAPTER  V. 

THE    CORRESPONDENCE    BETWEEN    LIFE    AND    ITS 
CIRCUMSTANCES. 

§  27.  WE  habitually  distinguish  between  a  live  object 
and  a  dead  one,  by  observing  whether  a  change  which  we 
make  in  the  surrounding  conditions,  or  one  which  Nature 
makes  in  them,  is  or  is  not  followed  by  some  perceptible 
change  in  the  object.  By  discovering  that  certain  things 
shrink  when  touched,  or  fly  away  when  approached,  or  start 
when  a  noise  is  made,  the  child  first  roughly  discriminates 
between  the  living  and  the  not-living;  and  the  man  when  in 
doubt  whether  an  animal  he  is  looking  at  is  dead  or  not,  stirs 
it  with  his  stick ;  or  if  it  be  at  a  distance,  shouts,  or  throws  a 
stone  at  it.  Vegetal  and  animal  life  are  alike  primarily 
recognized  by  this  process.  The  tree  that  puts  out  leaves 
when  the  spring  brings  increase  of  temperature,  the  flower 
which  opens  and  closes  with  the  rising  and  setting  of  the 
sun,  the  plant  that  droops  when  the  soil  is  dry  and  re-erects 
itself  when  watered,  are  considered  alive  because  of  these  in- 
duced changes;  in  common  with  the  acorn-shell  which  con- 
tracts when  a  shadow  suddenly  falls  on  it,  the  worm  that 
comes  to  the  surface  when  the  ground  is  continuously  shaken, 
and  the  hedgehog  that  rolls  itself  up  when  attacked. 

Not  only,  however,  do  we  look  for  some  response  when  an 
external  stimulus  is  applied  to  a  living  organism,  but  we 
expect  a  fitness  in  the  response.  Dead  as  well  as  living 
things  display  changes  under  certain  changes  of  condition: 
instance,  a  lump  of  carbonate  of  soda  that  effervesces  when 
dropped  into  sulphuric  acid;  a  cord  that  contracts  when 
wetted;  a  piece  of  bread  that  turns  brown  when  held  near 

91 


92 


THE   DATA   OF  BIOLOGY. 


the  fire.  But  in  these  cases,  we  do  not  see  a  connexion 
between  the  changes  undergone  and  the  preservation  of  the 
things  that  undergo  them;  or,  to  avoid  any  teleological  im- 
plication— the  changes  have  no  apparent  relations  to  future 
events  which  are  sure  or  likely  to  take  place.  In  vital 
changes,  however,  such  relations  are  manifest.  Light  being 
necessary  to  vegetal  life,  we  see  in  the  action  of  a  plant 
which,  when  much  shaded,  grows  towards  the  unshaded  side, 
an  appropriateness  which  we  should  not  see  did  it  grow 
otherwise.  Evidently  the  proceedings  of  a  spider  which 
rushes  out  when  its  web  is  gently  shaken  and  stays  within 
when  the  shaking  is  violent,  conduce  better  to  the  obtain- 
ment  of  food  and  the  avoidance  of  danger  than  were  they 
reversed.  The  fact  that  we  feel  surprise  when,  as  in  the  case 
of  a  bird  fascinated  by  a  snake,  the  conduct  tends  towards 
self-destruction,  at  once  shows  how  generally  we  have  observed 
an  adaptation  of  living  changes  to  changes  in  surrounding 
circumstances. 

A  kindred  truth,  rendered  so  familiar  by  infinite  repetition 
that  we  forget  its  significance,  must  be  named.  There  is 
invariably,  and  necessarily,  a  conformity  between  the  vital 
functions  of  any  organism  and  the  conditions  in  which  it  is 
placed — between  the  processes  going  on  inside  of  it  and  the 
processes  going  on  outside  of  it.  We  know  that  a  fish  can- 
not live  long  in  air,  or  a  man  under  water.  An  oak  growing 
in  the  ocean  and  a  seaweed  on  the  top  of  a  hill,  are  incredible 
combinations  of  ideas.  We  find  that  each  kind  of  animal  is 
limited  to  a  certain  range  of  climate ;  each  kind  of  plant  to 
certain  zones  of  latitude  and  elevation.  Of  the  marine  flora 
and  fauna,  each  species  is  found  only  between  such  and  such 
depths.  Some  blind  creatures  flourish  in  dark  caves;  the 
limpet  where  it  is  alternately  covered  and  uncovered  by  the 
tide;  the  red-snow  alga  rarely  elsewhere  than  in  the  arctic 
regions  or  among  alpine  peaks. 

Grouping  together  the  cases  first  named,  in  which  a  parti- 
cular change  in  the  circumstances  of  an  organism  is  followed 


CORRESPONDENCE  BETWEEN  LIFE  AND  ITS  CIRCUMSTANCES.    93 

by  a  particular  change  in  it,  and  the  cases  last  named,  in 
which  the  constant  actions  occurring  within  an  organism 
imply  some  constant  actions  occurring  without  it;  we  see 
that  in  both,  the  changes  or  processes  displayed  by  a  living 
body  are  specially  related  to  the  changes  or  processes  in  its 
environment.  And  here  we  have  the  needful  supplement  to 
our  conception  of  Life.  Adding  this  all-important  charac- 
teristic, our  conception  of  Life  becomes — The  definite  com- 
bination of  heterogeneous  changes,  both  simultaneous  and 
successive,  in  correspondence  with  external  co-existences  and 
sequences.  That  the  full  significance  of  this  addition  may  be 
seen,  it  will  be  necessary  to  glance  at  the  correspondence 
under  some  of  its  leading  aspects.* 

§  28.  Neglecting  minor  requirements,  the  actions  going 

*  Speaking  of  " the  general  idea  of  life"  M.  Comte  says : — " Cette  idee 
suppose,  en  effet,  non-seulement  celle  d'un  £tre  organise"  de  maniere  a  corn- 
porter  1'etat  vital,  mais  aussi  celle,  non  moins  indispensable,  d'un  certain 
ensemble  d'influences  extericures  propres  a  son  accomplissement.  Tine  telle 
harmonic  entre  1'etre  vivant  et  le  milieu  correspondent,  caractdrisc  evidem- 
ment  la  condition  fondamentale  de  la  vie."  Commenting  on  de  Blainville's 
definition  of  life,  which  he  adopts,  he  says : — "  Cette  lumineuse  definition  ne 
me  parait  laisser  rien  d'important  a  ddsirer,  si  ce  n'est  une  indication  plus 
directe  et  plus  explicite  de  ces  deux  conditions  fondamentales  co-relatives, 
n6cessairement  inseparables  de  1'etat  vivant,  un  organisme  determine^  et  un 
milieu  convenable."  It  is  strange  that  M.  Comte  should  have  thus  recog- 
nized the  necessity  of  a  harmony  between  an  organism  and  its  environment, 
as  a  condition  essential  to  life,  and  should  not  have  seen  that  the  continuous 
maintenance  of  such  inner  actions  as  will  counterbalance  outer  actions,  con- 
stitutes life. 

[When  the  original  edition  was  published  Dr.  J.  H.  Bridges  wrote  to  me 
saying  that  in  the  Politique  Positive,  Comte  had  developed  his  conception 
further.  On  p.  413,  denying  "le  prdtendu  antagonisme  des  corps  vivants 
envers  leurs  milieux  inorganiques,"  he  says  "  au  lieu  de  ce  conflit,  on  a  reconnu 
bientot  que  cette  relation  necessaire  constitue  une  condition  fondamentale  de 
la  vie  re'elle,  dont  la  notion  systdmatique  consiste  dans  une  intime  conciliation 
permanente  entre  la  spontandite  interieure  et  la  fatalite  exterieure."  Still, 
this  "conciliation  permanente'''1  seems  to  be  a  "condition'1''  to  life;  not  that 
varying  adjustment  of  changes  which  life  consists  in  maintaining.  In  presence 
of  an  ambiguity,  the  interpretation  which  agrees  with  his  previous  statement 
must  be  chosen.]  • 


94  THE   DATA   OF    BIOLOGY. 

on  in  a  plant  pre-suppose  a  surrounding  medium  containing 
at  least  carbonic  acid  and  water,  together  with  a  due  supply 
of  light  and  a  certain  temperature.  Within  the  leaves 
carbon  is  being  appropriated  and  oxygen  given  off;  without 
them,  is  the  gas  from  which  the  carbon  is  taken,  and  the 
imponderable  agents  that  aid  the  abstraction.  Be  the  nature 
of  the  process  what  it  may,  it  is  clear  that  there  are  external 
elements  prone  to  undergo  special  re-arrangements  under 
special  conditions.  It  is  clear  that  the  plant  in  sunshine 
presents  these  conditions  and  so  effects  these  re-arrange- 
ments. And  thus  it  is  clear  that  the  changes  which  pri- 
marily constitute  the  plant's  life,  are  in  correspondence  with 
co-existences  in  its  environment. 

If,  again,  we  ask  respecting  the  lowest  protozoon  how  it 
lives;  the  answer  is,  that  while  on  the  one  hand  its  substance 
is  undergoing  disintegration,  it  is  on  the  other  hand  absorbing 
nutriment;  and  that  it  may  continue  to  exist,  the  one  pro- 
cess must  keep  pace  with,  or  exceed,  the  other.  If  further 
we  ask  under  what  circumstances  these  combined  changes 
are  possible,  there  is  the  reply  that  the  medium  in  which  the 
protozoon  is  placed,  must  contain  oxygen  and  food — oxygen 
in  such  quantity  as  to  produce  some  disintegration ;  food  in 
such  quantity  as  to  permit  that  disintegration  to  be  made 
good.  In  other  words — the  two  antagonistic  processes  taking 
place  internally,  imply  the  presence  externally  of  materials 
having  affinities  that  can  give  rise  to  them. 

Leaving  those  lowest  animal  forms  which  simply  take  in 
through  their  surfaces  the  nutriment  and  oxygenated  fluids 
coming  in  contact  with  them,  we  pass  to  those  somewhat 
higher  forms  which  have  their  tissues  slightly  specialized.  In 
these  we  see  a  correspondence  between  certain  actions  in  the 
digestive  sac,  and  the  properties  of  certain  surrounding 
bodies.  That  a  creature  of  this  order  may  continue  to  live, 
it  is  necessary  not  only  that  there  be  masses  of  substance  in 
the  environment  capable  of  transformation  into  its  own  tis- 
sue, but  also  that  the  introduction  of  these  masses  into  its 


CORRESPONDENCE  BETWEEN  LIFE  AND  ITS  CIRCUMSTANCES.    95 

stomach,  shall  be  followed  by  the  secretion  of  a  solvent  fluid 
which  will  reduce  them  to  a  fit  state  for  absorption.  Special 
outer  properties  must  be  met  by  special  inner  properties. 

When,  from  the  process  by  which  food  is  digested,  we 
turn  to  the  process  by  which  it  is  seized,  the  same  general 
truth  faces  us.  The  stinging  and  contractile  power  of  a 
polype's  tentacle,  correspond  to  the  sensitiveness  and  strength 
of  the  creatures  serving  it  for  prey.  Unless  that  external 
change  which  brings  one  of  these  creatures  in  contact  with 
the  tentacle,  were  quickly  followed  by  those  internal  changes 
which  result  in  the  coiling  and  drawing  up  of  the  tentacle, 
the  polype  would  die  of  inanition.  The  fundamental  pro- 
cesses of  integration  and  disintegration  within  it,  would  get 
out  of  correspondence  with  the  agencies  and  processes  with- 
out it,  and  the  life  would  cease. 

Similarly,  when  the  creature  becomes  so  large  that  its 
tissue  cannot  be  efficiently  supplied  with  nutriment  by  mere 
absorption  through  its  lining  membrane,  or  duly  oxygenated 
by  contact  with  the  fluid  bathing  its  surface,  there  arises  a 
need  for  a  distributing  system  by  which  nutriment  and 
oxygen  may  be  carried  throughout  the  mass;  and  the  func- 
tions of  this  system,  being  subsidiary  to  the  two  primary 
functions,  form  links  in  the  correspondence  between  internal 
and  external  actions.  The  like  is  obviously  true  of  all  those 
subordinate  functions,  secretory  and  excretory,  that  facilitate 
oxidation  and  assimilation. 

Ascending  from  visceral  actions  to  muscular  and  nervous 
actions,  we  find  the  correspondence  displayed  in  a  manner 
still  more  obvious.  Every  act  of  locomotion  implies  the 
expenditure  of  certain  internal  forces,  adapted  in  amounts 
and  directions  to  balance  or  out-balance  certain  external 
forces.  The  recognition  of  an  object  is  impossible  without 
a  harmony  between  the  changes  constituting  perception,  and 
particular  properties  co-existing  in  the  environment.  Escape 
from  enemies  implies  motions  within  the  organism,  related  in 
kind  and  rapidity  to  motions  without  it.  Destruction  of 


96  THE   DATA   OF  BIOLOGY. 

prey  requires  a  special  combination  of  subjective  actions, 
fitted  in  degree  and  succession  to  overcome  a  group  of  objec- 
tive ones.  And  so  with  those  countless  automatic  processes 
constituting  instincts. 

In  the  highest  order  of  vital  changes  the  same  fact  is 
equally  manifest.  The  empirical  generalization  that  guides 
the  farmer  in  his  rotation  of  crops,  serves  to  bring  his  actions 
into  concord  with  certa\n  of  the  actions  going  on  in  plants 
and  soil.  The  rational  deductions  of  the  educated  navigator 
who  calculates  his  position  at  sea,  form  a  series  of  mental 
acts  by  which  his  proceedings  are  conformed  to  surrounding 
circumstances.  Alike  in  the  simplest  inferences  of  the  child 
and  the  most  complex  ones  of  the  man  of  science,  we  find  a 
correspondence  between  simultaneous  and  successive  changes 
in  the  organism,  and  co-existences  and  sequences  in  its  en- 
vironment. 

§  29.  This  general  formula  which  thus  includes  the  lowest 
vegetal  processes  along  with  the  highest  manifestations  of 
human  intelligence,  will  perhaps  call  forth  some  criticisms 
which  it  is  desirable  here  to  meet. 

It  may  be  thought  that  there  are  still  a  few  inorganic 
actions  included  in  the  definition;  as,  for  example,  that  dis- 
played by  the  mis-named  storm-glass.  The  feathery  crystal- 
lization which,  on  a  certain  change  of  temperature,  takes 
place  in  its  contained  solution,  and  which  afterwards  dis- 
solves to  reappear  in  new  forms  under  new  conditions,  may 
be  held  to  present  simultaneous  and  successive  changes  that 
are  to  some  extent  heterogeneous,  that  occur  with  some 
definiteness  of  combination,  and,  above  all,  occur  in  apparent 
correspondence  with  external  changes.  In  this  case  vegetal 
life  is  simulated  to  a  considerable  extent;  but  it  is  merely 
simulated.  The  relation  between  the  phenomena  occurring 
in  the  storm-glass  and  in  the  atmosphere  respectively,  is  not 
a  correspondence  at  all,  in  the  proper  sense  of  the  word.  Out- 
side there  is  a  thermal  change;  inside  there  is  a  change 


CORRESPONDENCE  BETWEEN  LIFE  AND  ITS  CIRCUMSTANCES.    97 

of  atomic  arrangement.  Outside  there  is  another  thermal 
change;  inside  there  is  another  change  of  atomic  arrange- 
ment. But  subtle  as  is  the  dependence  of  each  internal  upon 
each  external  change,  the  connexion  between  them  does  not, 
in  the  abstract,  differ  from  the  connexion  between  the  motion 
of  a  straw  and  the  motion  of  the  wind  that  disturbs  it.  In 
either  case  a  change  produces  a  change,  and  there  it  ends. 
The  alteration  wrought  by  some  environing  agency  on  this  or 
any  other  inanimate  object,  does  not  tend  to  induce  in  it  a 
secondary  alteration  which  anticipates  some  secondary  altera- 
tion in  the  environment.  But  in  every  living  body  there  is 
a  tendency  towards  secondary  alterations  of  this  nature ;  and 
it  is  in  their  production  that  the  correspondence  consists. 
The  difference  may  be  best  expressed  by  symbols.  Let  A  be 
a  change  in  the  environment,  and  B  some  resulting  change 
in  an  inorganic  mass.  Then  A  having  produced  B,  the 
action  ceases.  Though  the  change  A  in  the  environment  is 
followed  by  some  consequent  change  a  in  it;  no  parallel 
sequence  in  the  inorganic  mass  simultaneously  generates  in  it 
some  change  &  that  has  reference  to  the  change  a.  But  if 
we  take  a  living  body  of  the  requisite  organization,  and  let 
the  change  A  impress  on  it  some  change  C;  then,  while  in 
the  environment  A  is  occasioning  a,  in  the  living  body  C  will 
be  occasioning  c;  of  which  a  and  c  will  show  a  certain  con- 
cord in  time,  place,  or  intensity.  And  while  it  is  in  the 
continuous  production  of  such  concords  or  correspondences 
that  Life  consists,  it  is  ~by  the  continuous  production  of  them 
that  Life  is  maintained.  , 

The  further  criticism  to  be  expected  concerns  certain 
verbal  imperfections  in  the  definition,  which  it  seems  impos- 
sible to  avoid.  It  may  fairly  be  urged  that  the  word  corre- 
spondence will  not  include,  without  straining,  the  various 
relations  to  be  expressed  by  it.  It  may  be  asked : — How  can 
the  continuous  processes  of  assimilation  and  respiration  corre- 
spond with  the  co-existence  of  food  and  oxygen  in  the  environ- 
ment ?  or  again : — How  can  the  act  of  secreting  some  def en- 


98  THE   DATA   OF   BIOLOGY. 

sive  fluid  correspond  with  some  external  danger  which  may 
never  occur?  or  again: — How  can  the  dynamical  phenomena 
constituting  perception  correspond  with  the  statical  phe- 
nomena of  the  solid  body  perceived?  The  only  reply  is, 
that  we  have  no  word  sufficiently  general  to  comprehend  all 
forms  of  this  relation  between  the  organism  and  its  medium, 
and  yet  sufficiently  specific  to  convey  an  adequate  idea  of 
the  relation;  and  that  the  word  correspondence  seems  the 
least  objectionable.  The  fact  to  be  expressed  in  all  cases  is 
that  certain  changes,  continuous  or  discontinuous,  in  the 
organism,  are  connected  after  such  a  manner  that  in  their 
amounts,  or  variations,  or  periods  of  occurrence,  or  modes  of 
succession,  they  have  a  reference  to  external  actions,  constant 
or  serial,  actual  or  potential — a  reference  such  that  a  definite 
relation  among  any  members  of  the  one  group,  implies  a 
definite  relation  among  certain  members  of  the  other  group. 

§  30.  The  presentation  of  the  phenomena  under  this  gen- 
eral form,  suggests  that  our  conception  of  Life  may  be  reduced 
to  its  most  abstract  shape  by  regarding  its  elements  as  relations 
only.  If  a  creature's  rate  of  assimilation  is  increased  in  con- 
sequence of  a  decrease  of  temperature  in  the  environment,  it 
is  that  the  relation  between  the  food  consumed  and  the  heat 
produced,  is  so  re-adjusted  by  multiplying  both  its  members, 
that  the  altered  relation  in  the  environment  between  the 
quantity  of  heat  absorbed  from,  and  radiated  to,  bodies  of  a 
given  temperature,  is  counterbalanced.  If  a  sound  or  a  scent 
wafted  to  it  on  the  breeze  prompts  the  stag  to  dart  away 
from  the  deer-stalker,  it  is  that  there  exists  in  its  neighbour- 
hood a  relation  between  a  certain  sensible  property  and  cer- 
tain actions  dangerous  to  the  stag,  while  in  its  body  there 
exists  an  adapted  relation  between  the  impression  this  sensi- 
ble property  produces,  and  the  actions  by  which  danger  may 
be  escaped.  If  inquiry  has  led  the  chemist  to  a  law,  enabling 
him  to  tell  how  much  of  any  one  element  will  combine  with 
so  much  of  another,  it  is  that  there  has  been  established  in 


CORRESPONDENCE  BETWEEN  LIFE  AND  ITS  CIRCUMSTANCES.    99 

him  specific  mental  relations,  which  accord  with  specific 
chemical  relations  in  the  things  around.  Seeing,  then,  that 
in  all  cases  we  may  consider  the  external  phenomena  as  simply 
in  relation,  and  the  internal  phenomena  also  as  simply  in 
relation;  our  conception  of  Life  under  its  most  abstract 
aspect  will  be — The  continuous  adjustment  of  internal  rela- 
tions to  external  relations* 

While  it  is  simpler,  this  formula  has  the  further  advantage 
of  being  somewhat  more  comprehensive.  To  say  that  it  in- 
cludes not  only  those  definite  combinations  of  simultaneous 
and  successive  changes  in  an  organism,  which  correspond  to 
co-existences  and  sequences  in  the  environment,  but  also 
those  structural  arrangements  which  enable  the  organism  to 
adapt  its  actions  to  actions  in  the  environment,  is  going  too 
far;  for  though  these  structural  arrangements  present  in- 
ternal relations  adjusted  to  external  relations,  yet  the  con- 
tinuous adjustment  of  relations  cannot  be  held  to  include  a 
fixed  adjustment  already  made.  Life,  which  is  made  up  of 
dynamical  phenomena,  cannot  be  described  in  terms  that 
shall  at  the  same  time  describe  the  apparatus  manifesting  it, 
which  presents  only  statical  phenomena.  But  while  this 
antithesis  serves  to  remind  us  that  the  distinction  between 
the  organism  and  its  actions  is  as  wide  as  that  between 
Matter  and  Motion,  it  at  the  same  time  draws  attention  to 
the  fact  that,  if  the  structural  arrangements  of  the  adult  are 
not  properly  included  in  the  definition,  yet  the  developmental 
processes  by  which  those  arrangements  were  established,  are 
included.  For  that  process  of  evolution  during  which  the 
organs  of  the  embryo  are  fitted  to  their  prospective  func- 
tions, is  the  gradual  or  continuous  adjustment  of  internal 
relations  to  external  relations.  Moreover,  those  structural 
modifications  of  the  adult  organism  which,  under  change  of 
climate,  change  of  occupation,  change  of  food,  bring  about 
some  re-arrangement  in  the  organic  balance,  may  similarly 

*  In  further  elucidation  of  this  general  doctrine,  see  First  Principles, 


100  THE   DATA   OF  BIOLOGY. 

be  regarded  as  progressive  or  continuous  adjustments  of  in- 
ternal relations  to  external  relations.  So  that  not  only  does 
the  definition,  as  thus  expressed,  comprehend  all  those  activi- 
ties, bodily  and  mental,  which  constitute  our  ordinary  idea  of 
Life;  but  it  also  comprehends  both  those  processes  of  de- 
velopment by  which  the  organism  is  brought  into  general  fit- 
ness for  such  acti'vities,  and  those  after-processes  of  adapta- 
tion by  which  it  is  specially  fitted  to  its  special  activities. 

Nevertheless,  so  abstract  a  formula  as  this  is  scarcely 
fitted  for  our  present  purpose.  Reserving  it  for  use  where 
specially  appropriate,  it  will  be  best  commonly  to  employ  its 
more  concrete*  equivalent — to  consider  the  internal  relations 
as  "  definite  combinations  of  simultaneous  and  successive 
changes ; "  the  external  relations  as  "  co-existences  and  se- 
quences ; "  and  the  connexion  between  them  as  a  "  corre- 
spondence." 


CHAPTER  VI. 

THE    DEGREE    OF    LIFE   VARIES    AS    THE    DEGREE    OP 
CORRESPONDENCE. 

§  31.  ALREADY  it  has  been  shown  respecting  each  other 
component  of  the  foregoing  definition,  that  the  life  is  high  in 
proportion  as  that  component  is  conspicuous;  and  it  is  now 
to  be  remarked,  that  the  same  thing  is  especially  true  re- 
specting this  last  component- — the  correspondence  between 
internal  and  external  relations.  It  is  manifest,  a  priori,  that 
since  changes  in  the  physical  state  of  the  environment,  as 
also  of  those  mechanical  actions  and  those  variations  of 
available  food  which  occur  in  it,  are  liable  to  stop  the  pro- 
cesses going  on  in  the  organism;  and  since  the  adaptive 
changes  in  the  organism  have  the  effects  of  directly  or  in- 
directly counter-balancing  these  changes  in  the  environ- 
ment; it  follows  that  the  life  of  the  organism  will  be  short 
or  long,  low  or  high,  according  to  the  extent  to  which  changes 
in  the  environment  are  met  by  corresponding  changes  in  the 
organism.  Allowing  a  margin  for  perturbations,  the  life  will 
continue  only  while  the  correspondence  continues;  the  com- 
pleteness of  the  life  will  be  proportionate  to  the  complete- 
ness of  the  correspondence;  and  the  life  will  be  perfect  only 
when  the  correspondence  is  perfect.  Not  to  dwell  in  general 
statements,  however,  let  us  contemplate  this  truth  under  its 
concrete  aspects. 

§  32.    In  life  of  the  lowest  order  we  find  that  only  the  most 
prevalent  co-existences  and  sequences   in  the  environment, 
8  101 


102  TUB   DATA   OF  BIOLOGY. 

have  any  simultaneous  and  successive  changes  answering  to 
them  in  the  organism.  A  plant's  vital  processes  display 
adjustment  solely  to  the  continuous  co-existence  of  certain 
elements  and  forces  surrounding  its  roots  and  leaves;  and 
vary  only  with  the  variations  produced  in  these  elements  and 
forces  by  the  Sun — are  unaffected  by  the  countless  mechanical 
movements  and  contacts  occurring  around;  save  when  acci- 
dentally arrested  by  these.  The  life  of  a  worm  is  made  up  of 
actions  referring  to  little  else  than  the  tangible  properties  of 
adjacent  things.  All  those  visible  and  audible  changes 
which  happen  near  it,  and  are  connected  with  other  changes 
that  may  presently  destroy  it,  pass  unrecognized — produce  in 
it  no  adapted  changes:  its  only  adjustment  of  internal  rela- 
tions to  external  relations  of  this  order,  being  seen  when  it 
escapes  to  the  surface  on  feeling  the  vibrations  produced  by 
an  approaching  mole.  Adjusted  as  are  the  proceedings  of  a 
bird  to  a  far  greater  number  of  co-existences  and  sequences 
in  the  environment,  cognizable  by  sight,  hearing,  scent,  and 
their  combinations :  and  numerous  as  are  the  dangers  it  shuns 
and  the  needs  it  fulfils  in  virtue  of  this  extensive  correspond- 
ence; it  exhibits  no  such  actions  as  those  by  which  a  human 
being  counterbalances  variations  in  temperature  and  supply 
of  food,  consequent  on  the  seasons.  And  when  we  see  the 
plant  eaten,  the  worm  trodden  on,  the  bird  dead  from  starva- 
tion; we  see  alike  that  the  death  is  an  arrest  of  such  corre- 
spondence as  existed,  that  it  occurred  when  there  was  some 
change  in  the  environment  to  which  the  organism  made  no 
answering  change,  and  that  thus,  both  in  shortness  and  sim- 
plicity, the  life  was  incomplete  in  proportion  as  the  corre- 
spondence was  incomplete.  Progress  towards  more  prolonged 
and  higher  life,  evidently  implies  ability  to  respond  to  less 
general  co-existences  and  sequences.  Each  step  upwards  must 
consist  in  adding  to  the  previously-adjusted  relations  of 
actions  or  structures  which  the  organism  exhibits,  some 
further  relation  parallel  to  a  further  relation  in  the  environ- 
ment. And  the  greater  correspondence  thus  established,  must, 


DEGREE  OF  LIFE  VARIES  AS  DEGREE  OF  CORRESPONDENCE.  1Q3 

other  things  equal,  show  itself  both  in  greater  complexity  of 
life,  and  greater  length  of  life:  a  truth  which  will  be  fully 
perceived  on  remembering  the  enormous  mortality  which 
prevails  among  lowly-organized  creatures,  and  the  gradual 
increase  of  longevity  and  diminution  of  fertility  which  we 
meet  with  on  ascending  to  creatures  of  higher  and  higher 
developments. 

It  must  be  remarked,  however,  that  while  length  and  com- 
plexity of  life  are,  to  a  great  extent,  associated — while  a 
more  extended  correspondence  in  the  successive  changes 
commonly  implies  increased  correspondence  in  the  simul- 
taneous changes;  yet  it  is  not  uniformly  so.  Between  the 
two  great  divisions  of  life — animal  and  vegetal — this  contrast 
by  no  means  holds.  A  tree  may  live  a  thousand  years, 
though  the  simultaneous  changes  going  on  in  it  answer  only 
to  the  few  chemical  affinities  in  the  air  and  the  earth,  and 
though  its  serial  changes  answer  only  to  those  of  day  and 
night,  of  the  weather  and  the  seasons.  A  tortoise,  which 
exhibits  in  a  given  time  nothing  like  the  number  of  internal 
actions  adjusted  to  external  ones  that  are  exhibited  by  a  dog, 
yet  lives  far  longer.  The  tree  by  its  massive  trunk  and  the 
tortoise  by  its  hard  carapace,  are  saved  the  necessity  of 
responding  to  those  many  surrounding  mechanical  actions 
which  organisms  not  thus  protected  must  respond  to  or  die ; 
or  rather — the  tree  and  the  tortoise  display  in  their  struc- 
tures, certain  simple  statical  relations  adapted  to  meet 
countless  dynamical  relations  external  to  them.  But  not- 
withstanding the  qualifications  suggested  by  such  cases,  it 
needs  but  to  compare  a  microscopic  fungus  with  an  oak,  an 
animalcule  with  a  shark,  a  mouse  with  a  man,  to  recognize 
the  fact  that  this  increasing  correspondence  of  its  changes 
with  those  of  the  environment  which  characterizes  progress- 
ing life,  habitually  shows  itself  at  the  same  time  in  continuity 
and  in  complication. 

Even  were  not  the  connexion  between  length  of  life  and 
complexity  of  life  thus  conspicuous,  it  would  still  be  true 


104  THE   DATA   OF  BIOLOGY. 

that  the  life  is  great  in  proportion  as  the  correspondence  is 
great.  For  if  the  lengthened  existence  of  a  tree  be  looked 
upon  as  tantamount  to  a  considerable  amount  of  life;  then 
it  must  be  admitted  that  its  lengthened  display  of  corre- 
spondence is  tantamount  to  a  considerable  amount  of  corre- 
spondence. If,  otherwise,  it  be  held  that  notwithstanding  its 
much  shorter  existence,  a  dog  must  rank  above  a  tortoise  in 
degree  of  life  because  of  its  superior  activity;  then  it  is 
implied  that  its  life  is  higher  because  its  simultaneous  and 
successive  changes  are  more  complex  and  more  rapid — be- 
cause the  correspondence  is  greater.  And  since  we  regard 
as  the  highest  life  that  which,  like  our  own,  shows  great 
complexity  in  the  correspondences,  great  rapidity  in  the  suc- 
cession of  them,  and  great  length  in  the  series  of  them;  the 
equivalence  between  degree  of  life  and  degree  of  correspond- 
ence is  unquestionable. 

§33.  In  further  elucidation  of  this  general  truth,  and 
especially  in  explanation  of  the  irregularities  just  referred  to, 
it  must  be  pointed  out  that  as  the  life  becomes  higher  the 
environment  itself  becomes  more  complex.  Though,*  literally, 
the  environment  means  all  surrounding  space  with  the  co- 
existences and  sequences  contained  in  it:  yet,  practically,  it 
often  means  but  a  small  part  of  this.  The  environment  of 
an  entozoon  can  scarcely  be  said  to  extend  beyond  the  body 
of  the  animal  in  which  the  entozoon  lives.  That  of  a  fresh- 
water alga  is  virtually  limited  to  the  ditch  inhabited  by  the 
alga.  And,  understanding  the  term  in  this  restricted  sense, 
we  shall  see  that  the  superior  organisms  inhabit  the  more 
complicated  environments. 

Thus,  contrasted  with  the  life  found  on  land,  the  lower 
life  is  that  found  in  the  sea;  and  it  has  the  simpler  environ- 
ment. Marine  creatures  are  affected  by  fewer  co-existences 
and  sequences  than  terrestrial  ones.  Being  very  nearly  of 
the  same  specific  gravity  as  the  surrounding  medium,  they 
have  to  contend  with  less  various  mechanical  actions. 


DEGREE  OF  LIFE  VARIES  AS  DEGREE  OF  CORRESPONDENCE.  1Q5 

The  sea-anemone  fixed  to  a  stone,  and  the  acalephe 
borne  along  in  the  current,  need  to  undergo  no  internal 
changes  such  as  those,  by  which  the  caterpillar  meets  the 
varying  effects  of  gravitation,  while  creeping  over  and  under 
the  leaves.  Again,  the  sea  is  liable  to  none  of  those 

extreme  and  rapid  alterations  of  temperature  which  the  air 
suffers.  Night  and  day  produce  no  appreciable  modifications 
in  it;  and  it  is  comparatively  little  affected  by  the  seasons. 
Thus  its  contained  fauna  show  no  marked  correspondences 
similar  to  those  by  which  air-breathing  creatures  counter- 
balance thermal  changes.  Further,  in  respect  to  the 
supply  of  nutriment,  the  conditions  are  more  simple.  The 
lower  tribes  of  animals  inhabiting  the  water,  like  the  plants 
inhabiting  the  air,  have  their  food  brought  to  them.  The 
same  current  which  brings  oxygen  to  the  oyster,  also  brings 
it  the  microscopic  organisms  on  which  it  lives:  the  disinte- 
grating matter  and  the  matter  to  be  integrated,  co-exist  under 
the  simplest  relation.  It  is  otherwise  with  land  animals. 
The  oxygen  is  everywhere,  but  the  sustenance  is  not  every- 
where :  it  has  to  be  sought ;  and  the  conditions  under  which 
it  is  to  be  obtained  are  more  or  less  complex.  So 
too  with  that  liquid  by  the  agency  of  which  the  vital 
processes  are  carried  on.  To  marine  creatures  water  is 
ever  present,  and  by  the  lowest  is  passively  absorbed; 
but  to  most  creatures  living  on  the  earth  and  in  the  air,  it 
is  made  available  only  through  those  nervous  changes  consti- 
tuting perception,  and  those  muscular  ones  by  which  drinking 
is  effected.  Similarly,  after  tracing  upwards  from  the 
Amphibia  the  widening  extent  and  complexity  which  the 
environment,  as  practically  considered,  assumes — after  ob- 
serving further  how  increasing  heterogeneity  in  the  flora  and 
fauna  of  the  globe,  itself  progressively  complicates  the 
environment  of  each  species  of  organism — it  might  finally 
be  shown  that  the  same  general  truth  is  displayed  in  the 
history  of  mankind,  who,  in  the  course  of  their  progress, 
have  been  adding  to  their  physical  environment  a  social  en- 


106  THE   DATA    OF  BIOLOGY. 

vironment  that  has  been  growing  ever  more  involved.  Thus, 
speaking  generally,  it  is  clear  that  those  relations  in  'the  en- 
vironment to  which  relations  in  the  organism  must  corre- 
spond, themselves  increase  in  number  and  intricacy  as  the 
life  assumes  a  higher  form. 

§  34.  To  make  yet  more  manifest  the  fact  that  the  degree 
of. life  varies  as  the  degree  of  correspondence,  let  me  here 
point  out,  that  those  other  distinctions  successively  noted 
when  contrasting  vital  changes  with  non-vital  changes,  are 
all  implied  in  this  last  distinction — their  correspondence 
with  external  co-existences  and  sequences;  and  further,  that 
the  increasing  fulfilment  of  those  other  distinctions  which 
we  found  to  accompany  increasing  life,  is  involved  in  the 
increasing  fulfilment  of  this  last  distinction.  We  saw  that 
living  organisms  are  characterized  by  successive  changes,  and 
that  as  the  life  becomes  higher,  the  successive  changes  be- 
come more  numerous.  Well,  the  environment  is  full  of 
successive  changes,  and  the  greater  the  correspondence,  the 
greater  must  be  the  number  of  successive  changes  in  the 
organism.  We  saw  that  life  presents  simultaneous  changes, 
and  that  the  more  elevated  it  is,  the  more  marked  the  multi- 
plicity of  them.  Well,  besides  countless  co-existences  in  the 
environment,  there  are  often  many  changes  occurring  in  it  at 
the  same  moment;  and  hence  increased  correspondence  with 
it  implies  in  the  organism  an  increased  display  of  simul- 
taneous changes.  Similarly  with  the  heterogeneity  of  the 
changes.  In  the  environment  the  relations  are  very  varied 
in  their  kinds,  and  hence,  as  the  organic  actions  come  more 
and  more  into  correspondence  with  them,  they  too  must 
become  very  varied  in  their  kinds.  So  again  is  it  even 
with  definiteness  of  combination.  As  the  most  important 
surrounding  changes  with  which  each  animal  has  to  deal,  are 
the  definitely-combined  changes  exhibited  by  other  animals, 
whether  prey  or  enemies,  it  results  that  definiteness  of  com- 
bination must  be  a  general  characteristic  of  the  internal  ones 


DEGREE  OF  LIFE  VARIES  AS  DEGREE  OF  CORRESPONDENCE.  107 

which  have  to  coirespond  with  them.  So  that  throughout, 
the  correspondence  of  the  internal  relations  with  the  external 
ones  is  the  essential  thing ;  and  all  the  special  characteristics 
of  the  internal  relations,  are  but  the  collateral  results  of  this 
correspondence. 

§§  35,  36.  Before  closing  the  chapter,  it  will  be  useful  to 
compare  the  definition  of  Life  .here  set  forth,  with  the  defini- 
tion of  Evolution  set  forth  in  First  Principles.  Living 
bodies  being  bodies  which  display  in  the  highest  degree  the 
structural  changes  constituting  Evolution;  and  Life  being 
made  up  of  the  functional  changes  accompanying  these 
structural  changes;  we  ought  to  find  a  certain  harmony 
between  the  definitions  of  Evolution  and  of  Life.  Such  a 
harmony  is  not  wanting. 

The  first  distinction  we  noted  between  the  kind  of  change 
shown  in  Life,  and  other  kinds  of  change,  was  its  serial 
character.  We  saw  that  vital  change  is  substantially  unlike 
non-vital  change,  in  being  made  up  of  successive  changes. 
Xow  since  organic  bodies  display  so  much  more  than  inor- 
ganic bodies  those  continuous  differentiations  and  integrations 
which  constitute  Evolution;  and  since  the  re-distributions  of 
matter  thus  carried  so  far  in  a  comparatively  short  period, 
imply  concomitant  re-distributions  of  motion ;  it  is  clear  that 
in  a  given  time,  organic  bodies  must  undergo  changes  so 
comparatively  numerous  as  to  render  the  successiveness  of 
their  changes  a  marked  characteristic.  And  it  will  follow  a 
priori,  as  we  found  it  to  do  a  posteriori,  that  the  organisms 
exhibiting  Evolution  in  the  highest  degree,  exhibit  the 
longest  or  the  most  rapid  successions  of  changes,  or 
both.  Again,  it  was  shown  that  vital  change  is  dis- 

tinguished from  non- vital  change  by  being  made  up  of  many 
simultaneous  changes ;  and  also  that  creatures  possessing  high 
vitality  are  marked  off  from  those  possessing  low  vitality,  by 
the  far  greater  number  of  their  simultaneous  changes.  Here, 
too,  there  is  entire  congruity.  In  First  Principles,  §  156,  we 


108  THE   DATA   OF  BIOLOGY. 

reached  the  conclusion  that  a  force  falling  on  any  aggregate 
is  divided  into  several  forces;  that  when  the  aggregate  con- 
sists of  parts  that  are  unlike,  each  part  becomes  a  centre  of 
unlike  differentiations  of  the  incident  force;  and  that  thus 
the  multiplicity  of  such  differentiations  must  increase  with 
the  multiplicity  of  the  unlike  parts.  Consequently  organic 
aggregates,  which  as  a  class  are  distinguished  from  inorganic 
aggregates  by  the  greater  number  of  their  unlike  parts,  must 
be  also  distinguished  from  them  by  the  greater  number  of 
simultaneous  changes  they  display;  and,  further,  that  the 
higher  organic  aggregates,  having  more  numerous  unlike 
parts  than  the  lower,  must  undergo  more  numerous  simul- 
taneous changes.  We  next  found  that  the  changes 
occurring  in  living  bodies  are  contrasted  with  those  occurring 
in  other  bodies,  as  being  much  more  heterogeneous;  and  that 
the  changes  occurring  in  the  superior  living  bodies  are 
similarly  contrasted  with  those  occurring  in  inferior  ones. 
Well,  heterogeneity  of  function  is  the  correlate  of  hetero- 
geneity of  structure;  and  heterogeneity  of  structure  is  the 
leading  distinction  between  organic  and  inorganic  aggre- 
gates, as  well  as  between  the  more  highly  organized  and  the 
more  lowly  organized.  By  reaction,  an  incident  force  must 
be  rendered  multiform  in  proportion  to  the  multiformity  of 
the  aggregate  on  which  it  falls ;  and  hence  those  most  multi- 
form aggregates  which  display  in  the  highest  degree  the 
phenomena  of  Evolution  structurally  considered,  must  also 
display  in  the  highest  degree  the  multiform  actions  which 
constitute  Evolution  functionally  considered.  These 
heterogeneous  changes,  exhibited  simultaneously  and  in  suc- 
cession by  a  living  organism,  prove,  on  further  inquiry,  to  be 
distinguished  by  their  combination  from  certain  non-vital 
changes  which  simulate  them.  Here,  too,  the  parallelism  is 
maintained.  It  was  shown  in  First  Principles,  Chap.  XIV, 
that  an  essential  characteristic  of  Evolution  is  the  integration 
of  parts,  which  accompanies  their  differentiation — an  integra- 
tion shown  both  in  the  consolidation  of  each  part,  and  in  the 


DEGREE  OF  LIFE  VARIES  AS  DEGREE  OF  CORRESPONDENCE.  100 

union  of  all  the  parts  into  a  whole.  Hence,  animate  bodies 
having  greater  co-ordination  of  parts  than  inanimate  ones 
must  exhibit  greater  co-ordination  of  changes;  and  this 
greater  co-ordination  of  their  changes  must  not  only  dis- 
tinguish organic  from  inorganic  aggregates,  but  must,  for 
the  same  reason,  distinguish  higher  organisms  from  lower 
ones,  as  we  found  that  it  did.  Once  more,  it 

was  pointed  out  that  the  changes  constituting  Life  differ 
from  other  changes  in  the  definiteness  of  their  combination, 
and  that  a  distinction  like  in  kind  though  less  in  degree, 
holds  between  the  vital  changes  of  superior  creatures  and 
those  of  inferior  creatures.  These,  also,  are  contrasts  in  har- 
mony with  the  contrasts  disclosed  by  the  analysis  of  Evolu- 
tion. We  saw  (First  Principles,  §§  129-137)  that  during 
Evolution  there  is  an  increase  of  definiteness  as  well  as  an 
increase  of  heterogeneity.  We  saw  that  the  integration 
accompanying  differentiation  has  necessarily  the  effect  of 
increasing  the  distinctness  with  which  the  parts  are  marked 
off  from  each  other,  and  that  so,  out  of  the  incoherent  and 
indefinite  there  arises  the  coherent  and  definite.  But  a  co- 
herent whole  made  up  of  definite  parts  definitely  combined, 
must  exhibit  more  definitely  combined  changes  than  a  whole 
made  up  of  parts  that  are  neither  definite  in  themselves  nor 
in  their  combination.  Hence,  if  living  bodies  display  more 
than  other  bodies  this  structural  definiteness,  then  definite- 
ness  of  combination  must  be  a  characteristic  of  the  changes 
constituting  Life,  and  must  also  distinguish  the  vital 
changes  of  higher  organisms  from  those  of  lower  organ- 
isms. Finally,  we  discovered  that  all  these  peculi- 
arities are  subordinate  to  the  fundamental  peculiarity,  that 
vital  changes  take  place  in  correspondence  with  external 
co-existences  and  sequences,  and  that  the  highest  Life  is 
reached,  when  there  is  some  inner  relation  of  actions 
fitted  to  meet  every  outer  relation  of  actions  by  which 
the  organism  can  be  affected.  But  this  conception  of 
the  highest  Life,  is  in  harmony  with  the  conception,  before 


HO  THE  DATA  OP  BIOLOGY. 

arrived  at,  of  the  limit  of  Evolution.  When  treating  of 
equilibration  as  exhibited  in  organisms  (First  Principles, 
§§173,  174),  it  was  pointed  out  that  the  tendency  is  towards 
the  establishment  of  a  balance  between  inner  and  outer 
changes.  It  was  shown  that  "  the  final  structural  arrange- 
ments must  be  such  as  will  meet  all  the  forces  acting  on  the 
aggregate,  by  equivalent  antagonistic  forces,"  and  that  "  the 
maintenance  of  such  a  moving  equilibrium  "  as  an  organism 
displays,  "  requires  the  habitual  genesis  of  internal  forces 
corresponding  in  number,  directions,  and  amounts,  to  the 
external  incident  forces — as  many  inner  functions,  single  or 
combined,  as  there  are  single  or  combined  outer  actions  to  be 
met."  It  was  shown,  too,  that  the  relations  among  ideas  are 
ever  in  progress  towards  a  better  adjustment  between  mental 
actions  and  those  actions  in  the  environment  to  which  con- 
duct must  be  adjusted.  So  that  this  continuous  corre- 
spondence between  inner  and  outer  relations  which  consti- 
tutes Life,  and  the  perfection  of  which  is  the  perfection  of 
Life,  answers  completely  to  that  state  of  organic  moving 
equilibrium  which  we  saw  arises  in  the  course  of  Evolution 
and  tends  ever  to  become  more  complete. 


CHAPTER  VIA. 

THE    DYNAMIC     ELEMENT     IN     LIFE. 

§  36flv  A  CRITICAL  comparison  of  the  foregoing  formula 
with  the  facts  proves  it  to  be  deficient  in  more  ways  than 
one.  Let  us  first  look  at  vital  phenomena  which  are  not 
covered  by  it. 

Some  irritant  left  by  an  insect's  ovipositor,  sets  up  on  a 
plant  the  morbid  growth  named  a  gall.  The  processes  in  the 
gall  do  not  correspond  with  any  external  co-existences  or 
sequences  relevant  to  the  plant's  life — show  no  internal  rela- 
tions adjusted  to  external  relations.  Yet  we  cannot  deny 
that  the  gall  is  alive.  So,  too,  is  it  with  a  cancer  in  or  upon 
an  animal's  body.  The  actions  going  on  in  it  have  no  refer- 
ence, direct  or  indirect,  to  actions  in  the  environment.  Never- 
theless we  are  obliged  to  say  that  they  are  vital;  since  it 
grows  and  after  a  time  dies  and  decomposes. 

A  kindred  lesson  meets  us  when  from  pathological  evidence 
we  turn  to  physiological  evidence.  The  functions  of  some 
important  organs  may  still  be  carried  on  for  a  time  apart 
from  those  of  the  body  as  a  whole.  An  excised  liver,  kept 
at  a  fit  temperature  and  duly  supplied  with  blood,  secretes 
bile.  Still  more  striking  is  the  independent  action  of  the 
heart.  If  belonging  to  a  cold-blooded  animal,  as  a  frog, 
the  heart,  when  detached,  continues  to  beat,  even  until  its 
integuments  have  become  so  dry  that  they  crackle.  Now 
though  under  such  conditions  its  pulsations,  which  ordinarily 
form  an  essential  part  of  the  linked  processes  by  which  the 

111 


112  THE  DATA  OF  BIOLOGY. 

correspondence  between  inner  and  outer  actions  is  maintained, 
no  longer  form  part  of  such  processes,  we  must  admit  that 
the  continuance  of  them  implies  a  vital  activity. 

Embryological  changes  force  the  same  truth  upon  us. 
What  are  we  to  say  of  the  repeated  cell-fissions  by  which  in 
some  types  a  blastula,  or  mulberry-mass,  is  formed,  and  in 
other  types  a  blastoderm?  Neither  these  processes  nor  the 
structures  immediately  resulting  from  them,  show  any  corre- 
spondences with  co-existences  and  sequences  in  the  environ- 
ment; though  they  are  first  steps  towards  the  organization 
which  is  to  carry  on  such  correspondences.  Even  this  ex- 
tremely small  fulfilment  of  the  definition  is  absent  in  the 
cases  of  rudimentary  organs,  and  especially  those  rudimentary 
organs  which  after  being  partly  formed  are  absorbed.  No 
adjustment  can  be  alleged  between  the  inner  relations  which 
these  present  and  any  outer  relations.  The  outer  relations 
they  refer  to  ceased  millions  of  years  ago.  Yet  unquestion- 
ably the  changes  which  bring  about  the  production  and  ab- 
sorption of  these  futile  structures  are  vital  changes. 

Take  another  class  of  exceptions.  What  are  we  to  say  of 
a  laugh  ?  No  correspondence,  or  part  of  a  correspondence,  by 
which  inner  actions  are  made  to  balance  outer  actions,  can  be 
seen  in  it.  Or  again,  if,  while  working,  an  artisan  whistles, 
the  making  of  the  sounds  and  the  co-ordination  of  ideas  con- 
trolling them,  cannot  be  said  to  exhibit  adjustment  between 
certain  relations  of  thoughts,  and  certain  relations  of  things. 
Such  kinds  of  vital  activities  lie  wholly  outside  of  the  defini- 
tion given. 

But  perhaps  the  clearest  and  simplest  proof  is  yielded  by 
contrasting  voluntary  and  involuntary  muscular  actions. 
Here  is  a  hawk  adapting  its  changing  motions  to  the  chang- 
ing motions  of  a  pigeon,  so  as  eventually  to  strike  it:  the 
adjustment  of  inner  relations  to  outer  relations  is  manifest. 
Here  is  a  boy  in  an  epileptic  fit.  Between  his  struggles  and 
the  co-existences  and  sequences  around  him  there  is  no  corre- 
spondence whatever.  Yet  his  movements  betray  vitality  just 


THE  DYNAMIC  ELEMENT  IN  LIFE.  H3 

as  much  as  do  the  movements  of  the  hawk.  Both  exhibit  that 
principle  of  activity  which  constitutes  the  essential  element 
in  our  conception  of  life. 

§  36&.  Evidently,  then,  the  preceding  chapters  recognize 
only  the  form  of  our  conception  of  life  and  ignore  the  body 
of  it.  Partly  sufficing  as  does  the  definition  reached  to  express 
the  one,  it  fails  entirely  to  express  the  other.  Life  displays 
itself  in  ways  which  conform  to  the  definition;  but  it  also 
displays  itself  in  many  other  ways.  We  are  obliged  to  admit 
that  the  element  which  is  common  to  the  two  groups  of  ways 
is  the  essential  element.  The  essential  element,  then,  is  that 
special  kind  of  energy  seen  alike  in  the  usual  classes  of  vital 
actions  and  in  those  unusual  classes  instanced  above. 

Otherwise  presenting  the  contrast,  we  may  say  that  due 
attention  has  been  paid  to  the  connexions  among  the  mani- 
festations, while  no  attention  has  been  paid  to  that  which  is 
manifested.  When  it  is  said  that  life  is  "  the  definite  corre- 
spondence of  heterogeneous  changes,  both  simultaneous  and 
successive,  in  correspondence  with  external  co-existences  and 
sequences,"  there  arises  the  question — Changes  of  what? 
Within  the  body  there  go  on  many  changes,  mechanical, 
chemical,  thermal,  no  one  of  which  is  the  kind  of  change  in 
question;  and  if  we  combine  in  thought  so  far  as  we  can 
these  kinds  of  changes,  in  such  wise  that  each  maintains  its 
character  as  mechanical,  chemical,  or  thermal,  we  cannot  get 
out  of  them  the  idea  of  Life.  Still  more  clearly  do  we  see 
this  insufficiency  when  we  take  the  more  abstract  definition — 
"  the  continuous  adjustment  of  internal  relations  to  external 
relations."  Eelations  between  what  things?  is  the  question 
then  to  be  asked.  A  relation  of  which  the  terms  are  un- 
specified does  not  connote  a  thought  but  merely  the  blank 
form  of  a  thought.  Its  value  is  comparable  to  that  of  a 
cheque  on  which  no  amount  is  written.  If  it  be  said  that 
the  terms  cannot  be  specified  because  so  many  heterogeneous 
kinds  of  them  have  to  be  included,  then  there  comes  the 


114  THE  DATA  OF  BIOLOGY. 

reply  that  under  cover  of  this  inability  to  make  a  specifica- 
tion of  terms  that  shall  be  adequately  comprehensive,  there 
is  concealed  the  inability  to  conceive  the  required  terms  in 
any  way. 

Thus  a  critical  testing  of  the  definition  brings  us,  in  an- 
other way,  to  the  conclusion  reached  above,  that  that  which 
gives  the  substance  to  our  idea  of  Life  is  a  certain  unspecified 
principle  of  activity.  The  dynamic  element  in  life  is  its 
essential  element. 

§  36c.  Under  what  form  are  we  to  conceive  this  dynamic 
element?  Is  this  principle  of  activity  inherent  in  organic 
matter,  or  is  it  something  superadded  ?  Of  these  alternative 
suppositions  let  us  begin  with  the  last. 

As  I  have  remarked,  in  another  place,  the  worth  of  an 
hypothesis  may  be  judged  from  its  genealogy ;  and  so  judged 
the  hypothesis  of  an  independent  vital  principal  does  not 
commend  itself.  Its  history  carries  us  back  to  the  ghost- 
theory  of  the  savage.  Suggested  by  experiences  of  dreams, 
there  arises  belief  in  a  double — a  second  self  which  wanders 
away  during  sleep  and  has  adventures  but  comes  back  on 
waking ;  which  deserts  the  body  during  abnormal  insensibility 
of  one  or  other  kind;  and  which  is  absent  for  a  long  period 
at  death,  though  even  then  is  expected  eventually  to  return. 
This  indwelling  other-self,  which  can  leave  the  body  at  will, 
is  by-and-by  regarded  as  able  to  enter  the  bodies  of  fellow 
men  or  of  animals ;  or  again,  by  implication,  as  liable  to  have 
its  place  usurped  by  the  intruding  doubles  of  fellow  men, 
living  or  dead,  which  cause  fits  or  other  ills.  Along  with 
these  developments  its  quality  changes.  At  first  thought  of 
as  quite  material  it  is  gradually  de-materialized,  and  in  ad- 
vanced times  comes  to  be  regarded  as  spirit  or  breath;  as 
we  see  in  ancient  religious  books,  where  "  giving  up  the 
ghost "  is  shown  by  the  emergence  of  a  small  floating  figure 
from  the  mouth  of  a  dying  man.  This  indwelling  second 
self,  more  and  more  conceived  as  the  real  self  which  uses  the 


THE  DYNAMIC  ELEMENT  IN  LIFE.  H5 

body  for  its  purposes,  is,  with  the  advance  of  intelligence, 
still  further  divested  of  its  definite  characters;  and,  coming 
in  mediaeval  days  to  be  spoken  of  as  "  animal  spirits,"  ends  in 
later  days  in  being  called  a  vital  principle. 

Entirely  without  assignable  attributes,  this  something 
occurs  in  thought  not  as  an  idea  but  as  a  pseud-idea  (First 
Principles,,  Chap.  II).  It  is  assumed  to  be  representable  while 
really  unrepresentable.  We  need  only  insist  on  answers  to 
certain  questions  to  see  that  it  is  simply  a  name  for  an 
alleged  existence  which  has  not  been  conceived  and  cannot 
be  conceived. 

1.  Is  there  one  kind  of  vital  principle  for  all  kinds  of 
organisms,  or  is  there  a  separate  kind  for  each?  To  affirm 
the  first  alternative  is  to  say  that  there  is  the  same  vital 
principle  for  a  microbe  as  for  a  whale,  for  a  tape-worm  as  for 
the  person  it  inhabits,  for  a  protococcus  as  for  an  oak;  nay 
more — is  to  assert  community  of  vital  principle  in  the  think- 
ing man  and  the  unthinking  plant.  Moreover,  asserting 
unity  of  the  vital  principle  for  all  organisms,  is  reducing  it 
to  a  force  having  the  same  unindividualized  character  as  one 
of  the  physical  forces.  If,  on  the  other  hand,  different  kinds 
of  organisms  have  different  kinds  of  vital  principles,  these' 
must  be  in  some  way  distinguished  from  one  another.  How 
distinguished?  Manifestly  by  attributes.  Do  they  differ  in 
extension?  Evidently;  since  otherwise  that  which  animates 
the  vast  Sequoia  can  be  no  larger  than  that  which  animates  a 
yeast-plant,  and  to  carry  on  the  life  of  an  elephant  requires  a 
quantity  of  vital  principle  no  greater  than  that  required  for 
a  microscopic  monad.  Do  they  differ  otherwise  than  in 
amount?  Certainly;  since  otherwise  we  revert  to  the  pre- 
ceding alternative,  which  implies  that  the  same  quality  of 
vital  principle  serves  for  all  organisms,  simple  and  complex: 
the  vital  principle  is  a  uniform  force  like  heat  or  electricity. 
Hence,  then,  we  have  to  suppose  that  every  species  of  animal 
and  plant  has  a  vital  principle  peculiar  to  itself — a  principle 
adapted  to  use  the  particular  set  of  structures  in  which  it  is 


116  TEE  DATA  OF  BIOLOGY. 

contained.  But  dare  anyone  assert  this  multiplication  of 
vital  principles,  duplicating  not  only  all  existing  plants  and 
animals  but  all  past  ones,  and  amounting  in  the  aggregate  to 
some  millions? 

2.  How  are  we  to  conceive  that  genesis  of  a  vital  principle 
which  must  go  along  with  the  genesis  of  an  organism  ?    Here 
is  a  pollen-grain  which,  through  the  pistil,  sends  its  nucleus 
to  unite  with  the  nucleus  of  the  ovule;    or  here  are  the 
nuclei  of  spermatozoon  and  ovum,  which,  becoming  fused, 
initiate  a  new  animal :   in  either  case  failure  of  union  being 
followed  by  decomposition  of  the  proteid  materials,  while 
union   is    followed    by    development.      Whence    comes    that 
vital   principle   which   determines   the    organizing   process? 
Is  it  created  afresh  for  every  plant  and  animal?   or,  if  not, 
where  and  how  did  it  pre-exist?      Take  a  simpler  form  of 
this  problem.     A  protophyte  or  protozoon,  having  grown  to 
a  certain  size,  undergoes  a  series  of  complex  changes  ending 
in  fission.     In  its  undivided  state  it  had  a  vital  principle. 
What  of  its  divided  state?     The  parts  severally  swim  away, 
each  fully  alive,  each  ready  to  grow  and  presently  to  sub- 
divide, and  so  on  and  so  on,  until  millions  are  soon  formed. 
That  is  to  say,  there  is  a  multiplication  of  vital  principles  as 
of  the  protozoa  animated  by  them.     A  vital  principle,  then, 
both  divides  and  grows.     But  growth  implies  incorporation 
of  something.      What  does  the  vital  principle  incorporate? 
Is  it  some  other  vital  principle  external  to  it,  or  some  ma- 
terials out  of  which  more  vital  principle  is  formed?      And 
how,  in  either  case,  can  the  vital  principle  be  conceived  as 
other  than  a  material  something,  which  in  its  growth  and 
multiplication  behaves  just  as  visible  matter  behaves  ? 

3.  Equally  unanswerable  is  the  question  which  arises  in 
presence  of  life  that  has  become  latent.     Passing  over  the 
alleged  case  of  the  mummy  wheat,  the  validity  of  which  is 
denied,  there  is  experimental  proof  that  seeds  may,  under 
conditions  unfavourable  to  germination,  retain  for  ten,  twenty, 
and  some  even  for  thirty  years,  the  power  to  germinate  when 


THE  DYNAMIC  ELEMENT  IN  LIFE.  H? 

due  moisture  and  warmth  are  supplied.  (Cf.  Kerner's  Nat. 
Hist,  of  Plants,  i,  51-2).  Under  what  form  has  the  vital 
principle  existed  during  these  long  intervals?  It  is  a  prin- 
ciple of  activity.  In  this  case,  then,  the  principle  of  activity 
becomes  inactive.  But  how  can  we  conceive  an  inactive 
activity?  If  it  is  a  something  which  though  inactive  may 
be  rendered  active  when  conditions  favour,  we  are  introduced 
to  the  idea  of  a  vital  principle  of  which  the  vitality  may 
become  latent,  which  is  absurd.  What  shall  we  say  of  the 
desiccated  rotifer  which  for  years  has  seemed  to  be  nothing 
more  than  a  particle  of  dust,  but  which  now,  when  water  is 
supplied,  absorbs  it,  swells  up,  and  resumes  those  ciliary 
motions  by  which  it  draws  in  nutriment?  Was  the  vital 
principle  elsewhere  during  these  years  of  absolute  quies- 
cence? If  so,  why  did  it  come  back  at  the  right  moment? 
Was  it  all  along  present  in  the  rotifer  though  asleep?  How 
happened  it  then  to  awaken  at  the  time  when  the  supply  of 
water  enabled  the  tissues  to  resume  their  functions?  How 
happened  the  physical  agent  to  act  not  only  on  the  material 
substance  of  the  rotifer,  but  also  on  this  something  which  is 
not  a  material  substance  but  an  immaterial  source  of  activity  ? 
Evidently  neither  alternative  is  thinkable. 

Thus,  the  alleged  vital  principle  exists  in  the  minds  of 
those  who  allege  it  only  as  a  verbal  form,  not  as  an  idea; 
since  it  is  impossible  to  bring  together  in  consciousness  the 
terms  required  to  constitute  an  idea.  It  is  not  even  "  a  fig- 
ment of  imagination,"  for  that  implies  something  imaginable, 
but  the  supposed  vital  principle  cannot  even  be  imagined. 

§  36d.  When,  passing  to  the  alternative,  we  propose  to 
regard  life  as  inherent  in  the  substances  of  the  organisms 
displaying  it,  we  meet  with  difficulties  different  in  kind  but 
scarcely  less  in  degree.  The  processes  which  go  on  in  living 
things  are  incomprehensible  as  results  of  any  physical  actions 
known  to  us. 

Consider  one  of  the  simplest — that  presented  by  an  ordi- 


118  THE  DATA  OF  BIOLOGY. 

nary  vegetal  cell  forming  part  of  a  leaf  or  other  plant- 
structure.  Its  limiting  membrane,  originally  made  poly- 
hedral by  pressure  of  adjacent  cells,  Is  gradually  moulded 
"  into  one  of  cylindrical,  fibrous,  or  tabular  shape,  and 
strengthening  its  walls  with  pilasters,  borders,  ridges,  hooks, 
bands,  and  panels  of  various  kinds  "  (Kerner,  i,  43)  :  small 
openings  into  adjacent  cells  being  either  left  or  subsequently 
made.  Consisting  of  non-nitrogenous,  inactive  matters, 
these  structures  are  formed  by  the  inclosed  protoplast.  How 
formed?  Is  it  by  the  agency  of  the  nucleus?  But  the 
nucleus,  even  had  it  characters  conceivably  adapting  it  to 
this  function,  is  irregularly  placed;  and  that  it  should  work 
the  same  effects  upon  the  cell-wall  whether  seated  in  the 
middle,  at  one  end,  or  one  side,  is  incomprehensible.  Is  the 
protoplasm  then  the  active  agent?  But  this  is  arranged  into 
a  network  of  strands  and  threads  utterly  irregular  in  distri- 
bution and  perpetually  altering  their  shapes  and  connexions. 
Exercise  of  fit  directive  action  by  the  protoplasm  is  un- 
imaginable. 

Another  instance : — Consider  the  reproductive  changes  ex- 
hibited by  the  Spirogyra.  The  delicate  threads  which,  in 
this  low  type  of  Alga,  are  constituted  of  single  elongated 
cells  joined  end  to  end,  are  here  and  there  adjacent  to  one 
another;  and  from  a  cell  of  one  thread  and  a  cell  of  another 
at  fit  distance,  grow  out  prominences  which,  meeting  in  the 
interspace  and  forming  a  channel  by  the  dissolution  of  their 
adjoined  cell- walls,  empty  through  it  the  endochrome  of  the 
one  cell  into  the  other :  forming  by  fusion  of  the  two  a  zygote 
or  reproductive  body.  Under  what  influence  is  this  action 
initiated  and  guided?  There  is  no  conceivable  directive 
agency  in  either  cell  by  which,  when  conditions  are  fit,  a 
papilla  is  so  formed  as  to  meet  an  opposite  papilla. 

Or  again,  contemplate  the  still  more  marvellous  trans- 
formation occurring  in  Hydrodictyon  utriculosum.  United 
with  others  to  form  a  cylindrical  network,  each  sausage- 
shaped  cell  of  this  Alga  contains,  when  fully  developed,  a 


THE  DYNAMIC  ELEMENT  IN  LIFE.  H9 

lining  chromatophore  made  of  nucleated  protoplasm  with 
immersed  chlorophyll-grains.  This,  when  the  cell  is  adult, 
divides  into  multitudinous  zoospores,  which  presently  join 
their  ends  in  such  ways  as  to  form  a  network  with  meshes 
mostly  hexagonal,  minute  in  size,  but  like  in  arrangement  to 
the  network  of  which  the  parent  cell  formed  a  part.  Event- 
ually escaping  from  the  mother-cell,  this  network  grows  and 
presently  becomes  as  large  as  the  parent  network.  Under 
what  play  of  forces  do  these  zoospores  arrange  themselves 
into  this  strange  structure? 

Kindred  insoluble  problems  are  presented  by  animal  or- 
ganisms of  all  grades.  Of  microscopic  types  instance  the 
Coccospheres  and  Ehabdospheres  found  in  the  upper  strata  of 
sea-water.  Each  is  a  fragment  of  protoplasm  less  than  one- 
thousandth  of  an  inch  in  diameter,  shielded  by  the  elaborate 
protective  structures  it  has  formed.  The  elliptic  coccoliths 
of  the  first,  severally  having  a  definite  pattern,  unite  to  form 
by  overlapping  an  imbricated  covering;  and  of  the  other  the 
covering  consists  of  numerous  trumpet-mouthed  processes 
radiating  on  all  sides.  To  the  question — How  does  this 
particle  of  granular  protoplasm,  without  organs  or  definite 
structure,  make  for  itself  this  complicated  calcareous  ar- 
mour? there  is  no  conceivable  answer. 

Like  these  Protozoa,  the  lowest  Metazoa  do  things  which 
are  quite  incomprehensible.  Here  is  a  sponge  formed  of 
classes  of  monads  having  among  them  no  internuncial  appli- 
ances by  which  in  higher  types  cooperation  is  carried  on — 
flagellate  cells  that  produce  the  permeating  currents  of 
water,  flattened  cells  forming  protective  membranes,  and 
amrcboid  cells  lying  free  in  the  gelatinous  mesoderm.  These, 
without  apparent  concert,  build  up  not  only  the  horny  net- 
work constituting  the  chief  mass  of  their  habitation,  but  also 
embodied  spicules,  having  remarkable  symmetrical  forms. 
By  what  combined  influences  the  needful  processes  are 
effected,  it  is  impossible  to  imagine. 

If  we  turn  to  higher  types  of  Metazoa  in  which,  by  the 


120  THE  DATA  OF  BIOLOGY. 

agency  of  a  nervous  system,  many  cooperations  of  parts  are 
achieved  in  ways  that  are  superficially  comprehensible,  we 
".till  meet  with  various  actions  of  which  the  causation  cannot 
be  represented  in  thought.  Lacking  other  calcareous  matter, 
a  hen  picks  up  and  swallows  bits  of  broken  egg-shells;  and, 
occasionally,  a  cow  in  calf  may  be  seen  mumbling  a  bone  she 
has  found — evidently  scraping  off  with  her  teeth  some  of  its 
mass.  These  proceedings  have  reference  to  constitutional 
needs;  but  how  are  they  prompted?  What  generates  in  the 
cow  a  desire  to  bite  a  substance  so  unlike  in  character  to  her 
ordinary  food?  If  it  be  replied  that  the  blood  has  become 
poor  in  certain  calcareous  salts  and  that  hence  arises  the 
appetite  for  things  containing  them,  there  remains  the  ques- 
tion— How  does  this  deficiency  so  act  on  the  nervous  system 
as  to  generate  this  vague  desire  and  cause  the  movements 
which  satisfy  it?  By  no  effort  can  we  figure  to  ourselves  the 
implied  causal  processes. 

In  brief,  then,  we  are  obliged  to  confess  that  Life  in  its 
essence  cannot  be  conceived  in  physico-chemical  terms.  The 
required  principle  of  activity,  which  we  found  cannot  be 
represented  as  an  independent  vital  principle,  we  now  find 
cannot  be  represented  as  a  principle  inherent  in  living 
matter.  If,  by  assuming  its  inherence,  we  think  the  facts 
are  accounted  for,  we  do  but  cheat  ourselves  with  pseud- 
ideas. 

§  36e.  What  then  are  we  to  say — what  are  we  to  think  ? 
Simply  that  in  this  direction,  as  in  all  other  directions,  our 
explanations  finally  bring  us  face  to  face  with  the  inex- 
plicable. The  Ultimate  Reality  behind  this  manifestation,  as 
behind  all  other  manifestations,  transcends  conception.  It 
needs  but  to  observe  how  even  simple  forms  of  existence  are 
in  their  ultimate  natures  incomprehensible,  to  see  that  this 
most  complex  form  of  existence  is  in  a  sense  doubly  incom- 
prehensible. 

For  the  actions  of  that  which  the  ignorant  contemptuously 


THE  DYNAMIC  ELEMENT  IN  LIFE.  121 

call  brute  matter,  cannot  in  the  last  resort  be  understood  in 
their  genesis.  Were  it  not  that  familiarity  blinds  us,  the  fall 
of  a  stone  would  afford  matter  for  wonder.  Neither  Newton 
nor  anyone  since  his  day  has  been  able  to  conceive  how  the 
molecules  of  matter  in  the  stone  are  affected  not  only  by  the 
molecules  of  matter  in  the  adjacent  part  of  the  Earth  but  by 
those  forming  parts  of  its  mass  8,000  miles  off  which 
severally  exercise  their  influence  without  impediment  from 
intervening  molecules;  and  still  less  has  there  been  any  con- 
ceivable interpretation  of  the  mode  in  which  every  molecule 
of  matter  in  the  Sun,  92  millions  of  miles  away,  has  a  share 
in  controlling  the  movements  of  the  Earth.  What  goes  on 
in  the  space  between  a  magnet  and  the  piece  of  iron  drawn 
towards  it,  or  how  on  repeatedly  passing  a  magnet  along  a 
steel  needle  this,  by  some  change  of  molecular  state  as  we 
must  suppose,  becomes  itself  a  magnet  and  when  balanced 
places  its  poles  in  fixed  directions,  we  do  not  know.  And 
still  less  can  we  fathom  the  physical  process  by  which  an 
ordered  series  of  electric  pulses  sent  through  a  telegraph 
wire  may  be  made  to  excite  a  corresponding  series  of  pulses 
in  a  parallel  wire  many  miles  off. 

Turn  to  another  class  of  cases.  Consider  the  action  of  a 
surface  of  glass  struck  by  a  cathode  current  and  which  there- 
upon generates  an  order  of  rays  able  to  pass  through  solid 
matters  impermeable  to  light.  Or  contemplate  the  power 
possessed  by  uranium  and  other  metals  of  emitting  rays  im- 
perceptible by  our  eyes  as  light  but  which  yet,  in  what 
appears  to  us  absolute  darkness,  will,  if  passed  through  a 
camera,  produce  photographs.  Even  the  actions  of  one  kind 
of  matter  on  another  are  sufficiently  remarkable.  Here  is  a 
mass  of  gold  which,  after  the  addition  of  l-500th  part  of 
bismuth,  has  only  l-28th  of  the  tensile  strength  it  previously 
had;  and  here  is  a  mass  of  brass,  ordinarily  ductile  and 
malleable,  but  which,  on  the  addition  of  l-10,000th  part  of 
antimony,  loses  its  character.  More  remarkable  still  are  the 
influences  of  certain  medicines.  One-hundredth  of  a  grain 


122  THE  DATA  OP  BIOLOGY. 

of  nitre-glycerine  is  a  sufficient  dose.  Taking  an  average 
man's  weight  as  150  pounds,  it  results  that  his  body  is  appre- 
ciably affected  in  its  state  by  the  115-millionth  part  of  its 
weight  of  this  nitrogenous  compound. 

In  presence  of  such  powers  displayed  by'  matter  of  simple 
kinds  we  shall  see  how  impossible  it  is  even  to  imagine  those 
processes  going  on  in  organic  matter  out  of  which  emerges 
the  dynamic  element  in  Life.  As  no  separate  form  of  proteid 
possesses  vitality,  we  seem  obliged  to  assume  that  the  mole- 
cule of  protoplasm  contains  many  molecules  of  proteids,  pro- 
bably in  various  isomeric  states,  all  capable  of  ready  change 
and  therefore  producing  great  instability  of  the  aggregate 
they  form.  As  before  pointed  out  (§4),  a  proteid-molecule 
includes  more  than  220  equivalents  of  several  so-called  ele- 
ments. Each  of  these  undecomposed  substances  is  now  recog- 
nized by  chemists  as  almost  certainly  consisting  of  several 
kinds  of  components.  Hence  the  implication  is  that  a  proteid- 
molecule  contains  thousands  of  units,  of  which  the  different 
classes  have  their  respective  rates  of  inconceivably  rapid 
oscillation,  while  each  unit,  receiving  and  emitting  ethereal 
undulations,  affects  others  of  its  kind  in  its  own  and  adja- 
cent molecules :  an  immensely  complex  structure  having  im- 
mensely complex  activities.  And  this  complexity,  material 
and  dynamic,  in  the  proteid-molecule  we  must  regard  as 
raised  to  a  far  higher  degree  in  the  unit  of  protoplasm.  Here 
as  elsewhere  alternative  impossibilities  of  thought  present 
themselves.  We  find  it  impossible  to  think  of  Life  as  im- 
ported into  the  unit  of  protoplasm  from  without;  and  yet  we 
find  it  impossible  to  conceive  it  as  emerging  from  the  coopera- 
tion of  the  components. 

§  36/.  But  now,  having  confessed  that  Life  as  a  principle 
of  activity  is  unknown  and  unknowable — that  while  its  phe- 
nomena are  accessible  to  thought  the  implied  noumenon  is 
inaccessible — that  only  the  manifestations  come  within  the 
range  of  our  intelligence  while  that  which  is  manifested  lies 


THE  DYNAMIC  ELEMENT  IN  LIFE.  123 

beyond  it;  we  may  resume  the  conclusions  reached  in  the 
preceding  chapters.  Our  surface  knowledge  continues  to  be 
a  knowledge  valid  of  its  kind,  after  recognizing  the  truth  that 
it  is  only  a  surface  knowledge. 

For  the  conclusions  we  lately  reached  and  the  definition 
emerging  from  them,  concern  .the  order  existing  among  the 
actions  which  living  things  exhibit;  and  this  order  remains 
the  same  whether  we  know  or  do  not  know  the  nature  of 
that  from  which  the  actions  originate.  We  found  a  dis- 
tinguishing trait  of  Life  to  be  that  its  changes  display  a  cor- 
respondence with  co-existences  and  sequences  in  the  environ- 
ment; and  this  remains  a  distinguishing  trait,  though  the 
thing  which  changes  remains  inscrutable.  The  statement 
that  the  continuous  adjustment  of  internal  relations  to  ex- 
ternal relations  constitutes  Life  as  cognizable  by  us,  is  not 
invalidated  by  the  admission  that  the  reality  in  which  these 
relations  inhere  is  incognizable. 

Hence,  then,  after  duly  recognizing  the  fact  that,  as 
pointed  out  above,  Life,  even  phenomenally  considered,  is  not 
entirely  covered  by  the  definition,  since  there  are  various 
abnormal  manifestations  of  life  which  it  does  not  include,  we 
may  safely  accept  it  as  covering  the  normal  manifestations — 
those  manifestations  which  here  concern  us.  Carrying  with 
us  the  definition,  therefore  we  may  hereafter  use  it  for 
guidance  through  all  those  regions  of  inquiry  upon  which  we 
now  enter. 


CHAPTER  VII. 

THE    SCOPE    OF    BIOLOGY. 

§  37.  As  ordinarily  conceived,  the  science  of  Biology  falls 
into  two  great  divisions,  the  one  dealing  with  animal  life, 
called  Zoology,  and  the  other  dealing  with  vegetal  life, 
called  Botany,  or  more  properly  to  be  called  Phytology. 
But  convenient  as  is  this  division,  it  is  not  that  which  arises 
if  we  follow  the  scientific  method  of  including  in  one  group 
all  the  phenomena  of  fundamentally  the  same  order  and 
putting  separately  in  another  group  all  the  phenomena  of  a 
fundamentally  different  order.  For  animals  and  plants  are 
alike  in  having  structures;  and  animals  and  plants  are  alike 
in  having  functions  performed  by  these  structures;  and  the 
distinction  between  structures  and  functions  transcends  the 
difference  between  any  one  structure  and  any  other  or  be- 
tween any  one  function  and  any  other — is,  indeed,  an  absolute 
distinction,  like  that  between  Matter  and  Motion.  Recog- 
nizing, then,  the  logic  of  the  division  thus  indicated,  we 
must  group  the  parts  of  Biology  thus : — 

1.  An  account  of  the  structural  phenomena  presented  by 
organisms.    This  subdivides  into : — 

a.  The  established  structural  phenomena  presented  by 
individual  organisms. 

b.  The  changing  structural  phenomena  presented  by  suc- 
cessions of  organisms. 

2.  An  account  of  the  functional  phenomena  which  or- 
ganisms present.    This,  too,  admits  of  subdivision  into : — 

134 


THE  SCOPE  OF  BIOLOGY.  123 

a.  The  established  functional  phenomena  of  individual 

organisms. 
&.  The  changing  functional  phenomena  of  successions  of 

organisms. 

3  An  account  of  the  actions  of  Structures  on  Functions 
and  the  re-actions  of  Functions  on  Structures.  Like  the 
others,  this  is  divisible  into: — 

a.  The  actions  and  re-actions  as  exhibited  in  individual 

organisms. 
&.  The  actions  and  re-actions  as  exhibited  in  successions 

of  organisms. 

4.  An  account  of  the  phenomena  attending  the  production 
of  successions  of  organisms :  in  other  words — the  phenomena 
of  Genesis. 

Of  course,  for  purposes  of  exploration  and  teaching,  the 
division  into  Zoology  and  Botany,  founded  on  contrasts  so 
marked  and  numerous,  must  always  be  retained.  But  here 
recognizing  this  familiar  distinction  only  as  much  as  con- 
venience obliges  us  to  do,  let  us  now  pass  on  to  consider, 
more  in  detail,  the  classification  of  biologic  phenomena  above 
set  down  in  its  leading  outlines. 

§  38.  The  facts  of  structure  shown  in  an  individual 
organism,  are  of  two  chief  kinds.  In  order  of  conspicuous- 
ness,  though  not  in  order  of  time,  there  come  first  those 
arrangements  of  parts  which  characterize  the  mature  or- 
ganism; an  account  of  which,  originally  called  Anatomy,  is 
now  called  Morphology.  Then  come  those  successive  modifi- 
cations through  which  the  organism  passes  in  its  progress 
from  the  germ  to  the  developed  form;  an  account  of  which 
is  called  Embryology. 

The  structural  changes  which  any  series  of  individual 
organisms  exhibits,  admit  of  similar  classification.  On  the 
one  hand,  we  have  those  inner  and  outer  differences  of  shape, 
that  arise  between  the  adult  members  of  successive  genera- 
tions descended  from  a  common  stock — differences  which, 


12G  THE  DATA  OP  BIOLOGY. 

though  usually  not  marked  between  adjacent  generations, 
become  great  in  course  of  multitudinous  generations.  On 
the  other  hand,  we  have  those  developmental  modifications, 
seen  in  the  embryos,  through  which  such  modifications  of  the 
descended  forms  are  reached. 

Interpretation  of  the  structures  of  individual  organisms 
and  successions  of  organisms,  is  aided  by  two  subsidiary 
divisions  of  biologic  inquiry,  named  Comparative  Anatomy 
(properly  Comparative  Morphology)  and  Comparative  Em- 
bryology. These  cannot  be  regarded  as  in  themselves  parts 
of  Biology;  since  the  facts  embraced  under  them  are  not 
substantive  phenomena,  but  are  simply  incidental  to  sub- 
stantive phenomena.  All  the  truths  of  structural  Biology 
are  comprehended  under  the  two  foregoing  subdivisions; 
and  the  comparison  of  these  truths  as  presented  in  different 
classes  of  organisms,  is  simply  a  method  of  interpreting  them. 

Nevertheless,  though  Comparative  Morphology  and  Com- 
parative Embryology  do  not  disclose  additional  concrete 
facts,  they  lead  to  the  establishment  of  certain  abstract  facts. 
By  them  it  is  made  manifest  that  underneath  the  superficial 
differences  of  groups  and  classes  and  types  of  organisms, 
there  are  hidden  fundamental  similarities;  and  that  the 
courses  of  development  in  such  groups  and  classes  and  types, 
though  in  many  respects  divergent,  are  in  some  essential 
respects,  coincident.  The  wide  truths  thus  disclosed,  come 
under  the  heads  of  General  Morphology  and  General  Em- 
bryology. 

By  contrasting  organisms  there  is  also  achieved  that 
grouping  of  the  like  and  separation  of  the  unlike,  called 
Classification.  First  by  observation  of  external  characters; 
second  by  observation  of  internal  characters;  and  third  by 
observation  of  the  phases  of  development;  it  is  ascertained 
what  organisms  are  most  similar  in  all  respects;  what 
organisms  otherwise  unlike  are  like  in  important  traits; 
what  organisms  though  apparently  unallied  have  common 
primordial  characters.  Whence  there  results  such  an  ar- 


THE  SCOPE  OF  BIOLOGY.  127 

rangement  of  organisms,  that  if  certain  structural  attributes 
of  any  one  be  given,  its  other  structural  attributes  may  be 
empirically  predicted;  and  which  prepares  the  way  for  that 
interpretation  of  their  relations  and  genesis,  which  forms  an 
important  part  of  rational  Biology. 

§39.  The  second  main  division  of  Biology,  above  described 
as  embracing  the  functional  phenomena  of  organisms,  is  that 
which  is  in  part  signified  by  Physiology:  the  remainder 
being  distinguishable  as  Objective  Psychology.  Both  of  these 
fall  into  subdivisions  that  may  best  be  treated  separately. 

That  part  of  Physiology  which  is  concerned  with  the 
molecular  changes  going  on  in  organisms,  is  known  as 
Organic  Chemistry.  An  account  of  the  modes  in  which  the 
force  generated  in  organisms  by  chemical  change,  is  trans- 
formed into  other  forces,  and  made  to  work  the  various 
organs  that  carry  on  the  functions  of  Life,  comes  under  the 
head  of  Organic  Physics.  Psychology,  which  is 

mainly  concerned  with  the  adjustment  of  vital  actions  to 
actions  in  the  environment  (in  contrast  with  Physiology, 
which  is  mainly  concerned  with  vital  actions  apart  from 
actions  in  the  environment)  consists  of  two  quite  distinct 
portions.  Objective  Psychology  deals  with  those  functions 
of  the  nervo-muscular  apparatus  by  which  such  organisms 
as  possess  it  are  enabled  to  adjust  inner  to  outer  relations; 
and  includes  also  the  study  of  the  same  functions  as  exter- 
nally manifested  in  conduct.  Subjective  Psychology  deals 
with  the  sensations,  perceptions,  ideas,  emotions,  and  volitions 
that  are  the  direct  or  indirect  concomitants  of  this  visible 
adjustment  of  inner  to  outer  relations.  Consciousness  under 
its  different  modes  and  forms,  being  a  subject-matter  radically 
distinct  in  nature  from  the  subject-matter  of  Biology  in 
general;  and  the  method  of  self-analysis,  by  which  alone  the 
laws  of  dependence  among  changes  of  consciousness  can  be 
found,  being  a  method  unparalleled  by  anything  in  the  rest 
of  Biology;  we  are  obliged  to  regard  Subjective  Psychology 


128  THE  DATA  OF  BIOLOGY. 

as  a  separate  study.  And  since  it  would  be  very  incon- 
venient wholly  to  dissociate  Objective  Psychology  from  Sub- 
jective Psychology,  we  are  practically  compelled  to  deal  with 
the  two  as  forming  an  independent  science. 

Obviously,  the  functional  phenomena  presented  in  succes- 
sions of  organisms,  similarly  divide  into  physiological  and 
psychological.  Under  the  physiological  come  the 

modifications  of  bodily  actions  that  arise  in  the  course  of 
generations,  as  concomitants  of  structural  modifications ;  and 
these  may  be  modifications,  qualitative  or  quantitative,  in 
the  molecular  changes  classed  as  chemical,  or  in  the  organic 
actions  classed  as  physical,  or  in  both.  Under  the 

psychological  come  the  qualitative  and  quantitative  modifica- 
tions of  instincts,  feelings,  conceptions,  and  mental  processes 
in  general,  which  occur  in  creatures  having  more  or  less 
intelligence,  when  certain  of  their  conditions  are  changed. 
This,  like  the  preceding  department  of  Psychology,  has  in 
the  abstract  two  different  aspects — the  objective  and  the  sub- 
jective. Practically,  however,  the  objective,  which  deals  with 
these  mental  modifications  as  exhibited  in  the  changing 
habits  and  abilities  of  successive  generations  of  creatures,  is 
the  only  one  admitting  of  investigation;  since  the  corre- 
sponding alterations  in  consciousness  cannot  be  immediately 
known  to  any  but  the  subjects  of  them.  Evidently,  con- 
venience requires  us  to  join  this  part  of  Psychology  along 
with  the  other  parts  as  components  of  a  distinct  sub-science. 

Light  is  thrown  on  functions,  as  well  as  on  structures,  by 
comparing  organisms  of  different  kinds.  Comparative  Phy- 
siology and  Comparative  Psychology,  are  the  names  given  to 
those  collections  of  facts  respecting  the  homologies  and 
analogies,  bodily  and  mental,  disclosed  by  this  kind  of  in- 
quiry. These  classified  observations  concerning  likenesses 
and  differences  of  functions,  are  helpers  to  interpret  func- 
tions in  their  essential  natures  and  relations.  Hence  Com- 
parative Physiology  and  Comparative  Psychology  are  names 
of  methods  rather  than  names  of  true  subdivisions  of  Biology. 


THE  SCOPE  OP  BIOLOGY.  1^ 

Here,  however,  as  before,  comparison  of  special  truths, 
besides  facilitating  their  interpretation,  brings  to  light  certain 
general  truths.  Contrasting  functions  bodily  and  mental  as 
exhibited  in  various  kinds  of  organisms,  shows  that  there 
exists,  more  or  less  extensively,  a  community  of  processes 
and  methods.  Hence  result  two  groups  of  propositions  con- 
stituting General  Physiology  and  General  Psychology. 

§  40.  In  these  divisions  and  subdivisions  of  the  first  two 
great  departments  of  Biology,  facts  of  Structure  are  con- 
sidered separately  from  facts  of  Function,  so  far  as  separate 
treatment  of  them  is  possible.  The  third  great  department 
of  Biology  deals  with  them  in  their  necessary  connexions. 
It  comprehends  the  determination  of  functions  by  structures, 
and  the  determination  of  structures  by  functions. 

As  displayed  in  individual  organisms,  the  effects  of  struc- 
tures on  functions  are  to  be  studied,  not  only  in  the  broad 
fact  that  the  general  kind  of  life  an  organism  leads  is  neces- 
sitated by  the  main  characters  of  its  organization,  but  in  the 
more  special  and  less  conspicuous  fact,  that  between  mem- 
bers of  the  same  species,  minor  differences  of  structure  lead 
to  minor  differences  of  power  to  perform  certain  actions,  and 
of  tendencies  to  perform  such  actions.  Conversely, 

under  the  reactions  of  functions  on  structures  in  individual 
organisms,  come  the  facts  showing  that  functions,  when  ful- 
filled to  their  normal  extents,  maintain  integrity  of  structure 
in  their  respective  organs;  and  that  within  certain  limits 
increases  of  functions  are  followed  by  such  structural  changes 
in  their  respective  organs,  as  enable  them  to  discharge  better 
their  extra  functions. 

Inquiry  into  the  influence  of  structure  on  function  as  seen 
in  successions  of  organisms,  introduces  us  to  such  phenomena 
as  Mr.  Darwin's  Origin  of  Species  deals  with.  In  this  cate- 
gory come  all  proofs  of  the  general  truth,  that  when  an  in- 
dividual is  enabled  by  a  certain  structural  peculiarity  to  per- 
form better  than  others  of  its  species  some  advantageous 


130  THE  DATA  OP  BIOLOGY. 

action;  and  when  it  bequeaths  more  or  less  of  its  structural 
peculiarity  to  descendants,  among  whom  those  which  have  it 
most  markedly  are  best  able  to  thrive  and  propagate;  there 
arises  a  visibly  modified  type  of  structure,  having  a  more  or 
less  distinct  function.  In  the  correlative  class  of 

facts  (by  some  asserted  and  by  others  denied),  which  come 
under  the  category  of  reactions  of  function  on  structure  as 
exhibited  in  successions  of  organisms,  are  to  be  placed  all 
those  modifications  of  structure  which  arise  in  races,  when 
changes  of  conditions  entail  changes  in  the  balance  of  their 
functions — when  altered  function  externally  necessitated, 
produces  altered  structure,  and  continues  doing  this  through 
successive  generations. 

§  41.  The  fourth  great  division  of  Biology,  comprehending 
the  phenomena  of  Genesis,  may  be  conveniently  separated 
into  three  subdivisions. 

Under  the  first,  comes  a  description  of  all  the  special 
modes  whereby  the  multiplication  of  organisms  is  carried  on ; 
which  modes  range  themselves  under  the  two  chief  heads  of 
sexual  and  asexual.  An  account  of  Sexual  Multiplication 
includes  the  various  processes  by  which  germs  and  ova  are 
fertilized,  and  by  which,  after  fertilization,  they  are  furnished 
with  the  materials,  and  maintained  in  the  conditions,  needful 
for  their  development.  An  account  of  Asexual  Multiplica- 
tion includes  the  various  procesess  by  which,  from  the  same 
fertilized  germ  or  ovum,  there  are  produced  many  organisms 
partially  or  totally  independent  of  one  another. 

The  second  of  these  subdivisions  deals  with  the  phenomena 
of  Genesis  in  the  abstract.  It  takes  for  its  subject-matter 
such  general  questions  as — What  is  the  end  subserved  by  the 
union  of  sperm-cell  and  germ-cell?  Why  cannot  all  multi- 
plication be  carried  on  after  the  asexual  method?  What  are 
the  laws  of  hereditary  transmission?  What  are  the  causes 
of  variation? 

The  third  subdivision  is  devoted  to  still  more  abstract 


THE  SCOPE  OF  BIOLOGY.  131 

aspects  of  the  subject.  Recognizing  the  general  facts  of 
multiplication,  without  reference  to  their  modes  or  immediate 
causes,  it  concerns  itself  simply  with  the  different,  rates  of 
multiplication  in  different  kinds  of  organisms  and  different 
individuals  of  the  same  kind.  Generalizing  the. numerous 
contrasts  and  variations  of  fertility,  it  seeks  a  rationale  of 
them  in  their  relations  to  other  organic  phenomena. 

§  42.  Such  appears  to  be  the  natural  arrangement  of 
divisions  and  subdivisions  which  Biology  presents.  It  is, 
however,  a  classification  of  the  parts  of  the  science  when  fully 
developed;  rather  than  a  classification  of  them  as  they  now 
stand.  Some  of  the  subdivisions  above  named  have  no  recog- 
nized existence,  and  some  of  the  others  are  in  quite  rudi- 
mentary states.  It  is  impossible  now  to  fill  in,  even  in 
the  roughest  way,  more  than  a  part  of  the  outlines  here 
sketched. 

Our  course  of  inquiry  being  thus  in  great  measure  deter- 
mined by  the  present  state  of  knowledge,  we  are  compelled 
to  follow  an  order  widely  different  from  this  ideal  one.  It 
will  be  necessary  first  to  give  an  account  of  those  empirical 
generalizations  which  naturalists  and  physiologists  have 
established:  appending  to  those  which  admit  of  it,  such  de- 
ductive interpretations  as  First  Principles  furnishes  us  with. 
Having  done  this,  we  shall  be  the  better  prepared  for  dealing 
with  the  leading  truths  of  Biology  in  connexion  with  the 
doctrine  of  Evolution. 


PART  II. 

THE   INDUCTIONS   OF   BIOLOGY. 


CHAPTER   I. 

GROWTH. 

§  43.  PERHAPS  the  widest  and  most  familiar  induction  of 
Biology,  is  that  organisms  grow.  While,  however,  this  is  a 
characteristic  so  uniformly  and  markedly  displayed  by  plants 
and  animals,  as  to  be  carelessly  thought  peculiar  to  them, 
it  is  really  not  so.  Under  appropriate  conditions,  increase  of 
size  takes  place  in  inorganic  aggregates,  as  well  as  in  organic 
aggregates.  Crystals  grow;  and  often  far  more  rapidly  than 
living  bodies.  Where  the  requisite  materials  are  supplied  in 
the  requisite  forms,  growth  may  be  witnessed  in  non-crystal- 
line masses:  instance  the  fungous-like  accumulation  of 
carbon  that  takes  place  on  the  wick  of  an  urisnuffed  candle. 
On  an  immensely  larger  scale,  we  have  growth  in  geologic 
formations :  the  slow  accumulation  of  deposited  sediment  into 
a  stratum,  is  not  distinguishable  from  growth  in  its. widest 
acceptation.  And  if  we  go  back  to  the  genesis  of  celestial 
bodies,  assuming  them  to  have  arisen  by  Evolution,  these, 
too,  must  have  gradually  passed  into  their  concrete  shapes 
through  processes  of  growth.  Growth  is,  indeed,  as  being  an 
integration  of  matter,  the  primary  trait  of  Evolution;  and  if 
Evolution  of  one  kind  or  other  is  universal,  growth  is  uni- 
versal— universal,  that  is,  in  the  sense  that  all  aggregates 
display  it  in  some  way  at  some  period. 

The  essential  community  of  nature  between  organic 
growth  and  inorganic  growth,  is,  however,  most  clearly  seen 
on  observing  that  they  both  result  in  the  same  way.  The 
segregation  of  different  kinds  of  detritus  from  each  other,  as 

135 


136  THE  INDUCTIONS  OP  BIOLOGY. 

well  as  from  the  water  carrying  them,  and  their  aggregation 
into  distinct  strata,  is  but  an  instance  of  a  universal  tend- 
ency towards  the  union  of  like  units  and  the  parting  of  un- 
like units  (First  Principles,  §  163).  The  deposit  of  a  crystal 
from  a  solution  is  a  differentiation  of  the  previously  mixed 
molecules;  and  an  integration  of  one  class  of  molecules  into 
a  solid  body,  and  the  other  class  into  a  liquid  solvent.  Is 
not  the  growth  of  an  organism  an  essentially  similar  process  ? 
Around  a  plant  there  exist  certain  elements  like  the  elements 
which  form  its  substance;  and  its  increase  of  size  is  effected 
by  continually  integrating  these  surrounding  like  elements 
with  itself.  NOT  does  the  animal  fundamentally  differ  in 
this  respect  from  the  plant  or  the  crystal.  Its  food  is  a 
portion  of  the  environing  matter  that  contains  some  com- 
pound atoms  like  some  of  the  compound  atoms  constituting 
its  tissues;  and  either  through  simple  imbibition  or  through 
digestion,  the  animal  eventually  integrates  with  itself,  units 
like  those  of  which  it  is  built  up,  and  leaves  behind  the 
unlike  units.  To  prevent  misconception,  it  may  be 

well  to  point  out  that  growth,  as  here  defined,  must  be  dis- 
tinguished from  certain  apparent  and  real  augmentations 
of  bulk  which  simulate  it.  Thus,  the  long,  white  potato- 
shoots  thrown  out  in  the  dark,  are  produced  at  the  expense 
of  the  substances  which  the  tuber  contains:  they  illustrate 
not  the  accumulation  of  organic  matter,  but  simply  its  re- 
composition  and  re-arrangement.  Certain  animal-embryos, 
again,  during  their  early  stages,  increase  considerably  in  size 
without  assimilating  any  solids  from  the  environment;  and 
they  do  this  by  absorbing  the  surrounding  water.  Even  in  the 
highest  organisms,  as  in  children,  there  appears  sometimes  to 
occur  a  rapid  gain  in  dimensions  which  does  not  truly 
measure  the  added  quantity  of  organic  matter;  but  is  in  part 
due  to  changes  analogous  to  those  just  named.  Alterations 
of  this  kind  must  not  be  confounded  with  that  growth,  pro- 
perly so  called,  of  which  we  have  here  to  treat. 

The  next  general  fact  to  be  noted   respecting  organic 


GROWTH.  137 

growth,  is,  that  it  has  limits.  Here  there  appears  to  be  a 
distinction  between  organic  and  inorganic  growth;  but  this 
distinction  is  by  no  means  definite.  Though  that  aggrega- 
tion of  inanimate  matter  which  simple  attraction  produces, 
may  go  on  without  end;  yet  there  appears  to  be  an  end  to 
that  more  definite  kind  of  aggregation  which  results  from 
polar  attraction.  Different  elements  and  compounds  habitu- 
ally form  crystals  more  or  less  unlike  in  their  sizes ;  and  each 
seems  to  have  a  size  that  is  not  usually  exceeded  without  a 
tendency  arising  to  form  new  crystals  rather  than  to  increase 
the  old.  On  looking  at  the  organic  kingdom  as  a 

whole,  we  see  that  the  limits  between  which  growth  ranges 
are  very  wide  apart.  At  the  one  extreme  we  have  monads 
so  minute  as  to  be  rendered  but  imperfectly  visible  by  micro- 
scopes of  the  highest  power;  and  at  the  other  extreme  we 
have  trees  of  400  to  500  feet  high  and  animals  of  100  feet 
long.  It  is  true  that  though  in  one  sense  this  contrast  may 
be  legitimately  drawn,  yet  in  another  sense  it  may  not;  since 
these  largest  organisms  arise  by  the  combination  of  units 
which  are  individually  like  the  smallest.  A  single  plant  of  the 
genus  Protococcus,  is  of  the  same  essential  structure  as  one  of 
the  many  cells  united  to  form  the  thallus  of  some  higher 
Alga,  or  the  leaf  of  a  phaenogam.  Each  separate  shoot  of  a 
phaenogam  is  usually  the  bearer  of  many  leavqg.  And  a 
tree  is  an  assemblage  of  numerous  united  shoots.  One  of 
these  great  teleophytes  is  thus  an  aggregate  of  aggregates  of 
aggregates  of  units,  which  severally  resemble  protophytes  in 
their  sizes  and  structures ;  and  a  like  building  up  is  traceable 
throughout  a  considerable  part  of  the  animal  kingdom. 
Even,  however,  when  we  bear  in  mind  this  qualification,  and 
make  our  comparisons  between  organisms  of  the  same  degree 
of  composition,  we  still  find  the  limit  of  growth  to  have  a 
great  range.  The  smallest  branched  flowering  plant  is  ex- 
tremely insignificant  by  the  side  of  a  forest  tree;  and  there 
is  an  enormous  difference  in  bulk  between  the  least  and  the 
greatest  mammal.  But  on  comparing  members  of  the 


138  THE   INDUCTIONS  OF   BIOLOGY. 

same  species,  we  discover  the  limit  of  growth  to  be  much 
less  variable.  Among  the  Protozoa  and  Protophyta,  each 
kind  has  a  tolerably  constant  adult  size ;  and  among  the  most 
complex  organisms  the  differences  between  those  of  the  same 
kind  which  have  reached  maturity,  are  usually  not  very 
great.  The  compound  plants  do,  indeed,  sometimes  present 
marked  contrasts  between  stunted  and  well-grown  individ- 
uals ;  but  the  higher  animals  diverge  but  inconsiderably  from 
the  average  standards  of  their  species. 

On  surveying  the  facts  with  a  view  of  empirically  general- 
izing the  causes  of  these  differences,  we  are  soon  made  aware 
that  by  variously  combining  and  conflicting  with  one  another, 
these  causes  produce  great  irregularities  of  result.  It  becomes 
manifest  that  no  one  of  them  can  be  traced  to  its  conse- 
quences, unqualified  by  the  rest.  Hence  the  several  state- 
ments contained  in  the  following  paragraphs  must  be  taken 
as  subject  to  mutual  modification. 

Let  us  consider  first  the  connexion  between  degree  of 
growth  and  complexity  of  structure.  This  connexion,  being 
involved  with  many  others,  becomes  apparent  only  on  so 
averaging  the  comparisons  as  to  eliminate  differences  among 
the  rest.  Nor  does  it  hold  at  all  where  the  conditions  are 
radically  dissimilar,  as  between  plants  and  animals.  But 
bearing  in  mind  these  qualifications,  we  shall  see  that 
organization  has  a  determining  influence  on  increase  of 
mass.  Of  plants  the  lowest,  classed  as  Thallophytes, 

usually  attain  no  considerable  size.  Alga?,  Fungi,  and  the 
Lichens  formed  by  association  of  them  count  among  their 
numbers  but  few  bulky  species:  the  largest,  such  a8  certain 
Algae  found  in  antarctic  seas,  not  serving  greatly  to  raise  the 
average;  and  these  gigantic  seaweeds  possess  a  considerable 
complexity  of  histological  organization  very  markedly  ex- 
ceeding that  of  their  smaller  allies.  Though  among  Bryo- 
phytes  and  Pteridophytes  there  are  some,  as  the  Tree-ferns, 
which  attain  a  considerable  height,  the  majority  are  but  of 
humble  growth.  The  Monocotyledons,  including  at  one 


GROWTH.  139 

extreme  small  grasses  and  at  the  other  tall  palms,  show  us  an 
average  and  a  maximum  greater  than  that  reached  by  the 
Pteridophytes.  And  the  Monocotyledons  are  exceeded  by 
the  Dicotyledons;  among  which  are  found  the  monarchs  of 
the  vegetal  kingdom.  Passing  to  animals,  we  meet 

the  fact  that  the  size  attained  by  Vertebrata  is  usually  much 
greater  than  the  size  attained  by  Invertebrata.  Of  inverte- 
brate animals  the  smallest,  classed  as  Protozoa,  are  also  the 
simplest;  and  the  largest,  belonging  to  the  Annulosa  and 
Mollusca,  are  among  the  most  complex  of  their  respective 
types.  Of  vertebrate  animals  we  see  that  the  greatest  are 
Mammals,  and  that  though,  in  past  epochs,  there  were  Rep- 
tiles of  vast  bulks,  their  bulks  did  not  equal  that  of  the 
whale:  the  great  Dinosaurs,  though  as  long,  being  nothing 
like  as  massive.  Between  reptiles  and  birds,  and  between 
land-vertebrates  and  water-vertebrates,  the  relation  does  not 
hold :  the  conditions  of  existence  being  in  these  cases  widely 
different.  But  among  fishes  as  a  class,  and  among  reptiles  as 
a  class,  it  is  observable  that,  speaking  generally,  the  larger 
species  are  framed  on  the  higher  types.  The  critical 

reader,  who  has  mentally  checked  these  statements  in  pass- 
ing them,  has  doubtless  already  seen  that  this  relation  is 
not  a  dependence  of  organization  on  growth  but  a  dependence 
of  growth  on  organization.  The  majority  of  Dicotyledons 
are  smaller  than  some  Monocotyledons;  many  Monocotyle- 
dons are  exceeded  in  size  by  certain  Pteridophytes;  and 
even  among  Thallophytes,  the  least  developed  among  com- 
pound plants,  there  are  kinds  of  a  size  which  many  plants  of 
the  highest  order  do  not  reach.  Similarly  among  animals. 
There  are  plenty  of  Crustaceans  less  than  Actiniae;  nume- 
rous reptiles  are  smaller  than  some  fish;  the  majority  of 
mammals  are  inferior  in  bulk  to  the  largest  reptiles ;  and  in 
the  contrast  between  a  mouse  and  a  well-grown  Medusa,  we 
see  a  creature  that  is  elevated  in  type  of  structure  exceeded 
in  mass  by  one  that  is  extremely  low.  Clearly  then,  it  cannot 
be  held  that  high  organization  is  habitually  accompanied  by 


140  THE  INDUCTIONS  OP  BIOLOGY. 

great  size.  The  proposition  here  illustrated  is  the  converse 
one,  that  great  size  is  habitually  accompanied  by  high 
organization.  The  conspicuous  facts  that  the  largest  species 
of  both  animals  and  vegetals  belong  to  the  highest  classes, 
and  that  throughout  their  various  sub-classes  the  higher 
usually  contain  the  more  bulky  forms,  show  this  connexion 
as  clearly  as  we  can  expect  it  to  be  shown,  amid  so  many 
modifying  causes  and  conditions. 

The  relation  between  growth  and  supply  of  available 
nutriment,  is  too  familiar  a  relation  to  need  proving.  There 
are,  however,  some  aspects  of  it  that  must  be  contemplated  be- 
fore its  implications  can  be  fully  appreciated.  Among 
plants,  which  are  all  constantly  in  contact  with  the  gaseous, 
liquid,  and  solid  matters  to  be  incorporated  with  their  tissues, 
and  which,  in  the  same  locality,  receive  not  very  unlike 
amounts  of  light  and  heat,  differences  in  the  supplies  of 
available  nutriment  have  but  a  subordinate  connexion  with 
differences  of  growth.  Though  in  a  cluster  of  herbs  spring- 
ing up  from  the  seeds  let  fall  by  a  parent,  the  greater  sizes 
of  some  than  of  others  is  doubtless  due  to  better  nutrition, 
consequent  on  accidental  advantages;  yet  no  such  inter- 
pretation can  be  given  of  the  contrast  in  size  between  these 
herbs  and  an  adjacent  tree.  Other  conditions  here  come 
into  play:  one  of  the  most  important  being,  an  absence  in 
the  one  case,  and  presence  in  the  other,  of  an  ability  to 
secrete  such  a  quantity  of  ligneous  fibre  as  will  produce  a 
stem  capable  of  supporting  a  large  growth.  Among 
animals,  however,  which  (excepting  some  Entozoa)  differ 
from  plants  in  this,  that  instead  of  bathing  their  surfaces 
the  matters  they  subsist  on  are  dispersed,  and  have  to  be 
obtained,  the  relation  between  available  food  and  growth 
is  shown  with  more  regularity.  The  Protozoa)  living  on 
microscopic  fragments  of  organic  matter  contained  in  the 
surrounding  water,  are  unable,  during  their  brief  lives,  to 
accumulate  any  considerable  quantity  of  nutriment.  Polyzoa, 
having  for  food  these  scarcely  visible  members  of  the  animal 


GROWTH.  141 

kingdom,  are,  though  large  compared  with  their  prey,  small 
as  measured  by  other  standards;  even  when  aggregated  into 
groups  of  many  individuals,  which  severally  catch  food  for 
the  common  weal,  they  are  often  so  inconspicuous  as  readily 
to  be  passed  over  by  the  unobservant.  And  if  from  this 
point  upwards  we  survey  the  successive  grades  of  animals,  it 
becomes  manifest  that,  in  proportion  as  the  size  is  great,  the 
masses  of  nutriment  are  either  large,  or,  what  is  practically 
the  same  thing,  are  so  abundant  and  so  grouped  that  large 
quantities  may  be  readily  taken  in.  Though,  for  example,  the 
greatest  of  mammals,  the  arctic  whale,  feeds  on  such  com- 
paratively small  creatures  as  the  acalephes  and  molluscs 
floating  in  the  seas  it  inhabits,  its  method  of  gulping  in 
whole  shoals  of  them  and  filtering  away  the  accompanying 
water,  enables  it  to  secure  great  quantities  of  food.  We 
may  then  with  safety  say  that,  other  things  equal,  the 
growth  of  an  animal  depends  on  the  abundance  and  sizes  of 
the  masses  of  nutriment  which  its  powers  enable  it  to  appro- 
priate. Perhaps  it  may  be  needful  to  add  that,  in 
interpreting  this  statement,  the  proportion  of  competitors 
must  be  taken  into  account.  Clearly,  not  the  absolute,  but 
the  relative,  abundance  of  fit  food  is  the  point;  and  this 
relative  abundance  very  much  depends  on  the  number  of 
individuals  competing  for  the  food.  Thus  all  who  have  had 
experience  in  fishing  in  Highland  lochs,  know  that  where 
the  trout  are  numerous  they  are  small,  and  that  where  they 
are  comparatively  large  they  are  comparatively  few. 

What  is  the  relation  between  growth  and  expenditure  of 
energy?  is  a  question  which  next  presents  itself.  Though 
there  is  reason  to  believe  such  a  relation  exists,  it  is  not  very 
readily  traced:  involved  as  it  is  with  so  many  other  rela- 
tions. Some  contrasts,  however,  may  be  pointed  out  that 
appear  to  give  evidence  of  it.  Passing  over  the  vegetal 
kingdom,  throughout  which  the  expenditure  of  force  is  too 
small  to  allow  of  such  a  relation  being  visible,  let  us  seek  in 
the  animal  kingdom,  some  case  where  classes  otherwise 


142  THE  INDUCTIONS  OF  BIOLOGY. 

allied,  arc  contrasted  in  their  locomotive  activities.  Let  us 
compare  birds  on  the  one  hand,  with  reptiles  and  mammals 
on  the  other.  It  is  an  accepted  doctrine  that  birds  are 
organized  on  a  type  closely  allied  to  the  reptilian  type,  but 
superior  to  it;  and  though  in  some  respects  the  organization 
of  birds  is  inferior  to  that  of  mammals,  yet  in  other  respects, 
as  in  the  greater  heterogeneity  and  integration  of  the  skeleton, 
the  more  complex  development  of  the  respiratory  system, 
and  the  higher  temperature  of  the  blood,  it  may  be  held 
that  birds  stand  above  mammals.  Hence  were  growth  de- 
pendent only  on  organization,  we  might  infer  that  the  limit 
of  growth  among  birds  should  not  be  much  short  of  that 
among  mammals;  and  that  the  bird-type  should  admit  of  a 
larger  growth  than  the  reptile-type.  Again,  we  see  no  mani- 
fest disadvantages  under  which  birds  labour  in  obtaining 
food,  but  from  which  reptiles  and  mammals  are  free.  On  the 
contrary,  birds  are  able  to  get  at  food  that  is  fixed  beyond 
the  reach  of  reptiles  and  mammals;  and  can  catch  food  that 
is  too  swift  of  movement  to  be  ordinarily  caught  by  reptiles 
and  mammals.  Nevertheless,  the  limit  of  growth  in  birds 
falls  far  below  that  reached  by  reptiles  and  mammals.  With 
what  other  contrast  between  these  classes,  is  this  contrast 
connected?  May  we  not  suspect  that  it  is  connected  (par- 
tially though  not  wholly)  with  the  contrast  between  their 
amounts  of  locomotive  exertion  ?  Whereas  mammals  (except- 
ing bats,  which  are  small),  are  during  all  their  movements 
supported  by  solid  surfaces  or  dense  liquids;  and  whereas 
reptiles  (excepting  the  ancient  pterodactyles,  which  were  not 
very  large),  are  similarly  restricted  in  their  spheres  of  move- 
ment; the  majority  of  birds  move  more  or  less  habitually 
through  a  rare  medium,  in  which  they  cannot  support  them- 
selves without  relatively  great  efforts.  And  this  general  fact 
may  be  joined  with  the  special  fact,  that  those  members  of 
the  class  Aves,  as  the  Dinornis  and  Epiornis,  which  ap- 
proached in  size  to  the  larger  Mammalia  and  Reptilia,  were 
creatures  incapable  of  flight — creatures  which  did  not  expend 


GROWTH.  143 

this  excess  of  force  in  locomotion.  But  as  implied  above,  and 
as  will  presently  be  shown,  another  factor  of  importance  comes 
into  play;  so  that  perhaps  the  safest  evidence  that  there  is 
an  antagonism  between  the  increase  of  bulk  and  the  quan- 
tity of  motion  evolved  is  that  supplied  by  the  general  experi- 
ence, that  human  beings  and  domestic  animals,  when  over- 
worked while  growing,  are  prevented  from  attaining  the  ordi- 
nary dimensions. 

One  other  general  truth  concerning  degrees  of  growth, 
must  be  set  down.  It  is  a  rule,  having  exceptions  of  no 
great  importance,  that  large  organisms  commence  their 
separate  existences  as  masses  of  organic  matter  more  or  less 
considerable  in  size,  and  commonly  with  organizations  more 
or  less  advanced;  and  that  throughout  each  organic  sub- 
kingdom,  there  is  a  certain  general,  though  irregular,  relation 
between  the  initial  and  the  final  bulks.  Vegetals 

exhibit  this  relation  less  manifestly  than  animals.  Yet 
though,  among  the  plants  that  begin  life  as  minute  spores, 
there  are  some  which,  by  the  aid  of  an  intermediate  form, 
grow  to  large  sizes,  the  immense  majority  of  them  remain 
small.  While,  conversely,  the  great  Monocotyledons  and 
Dicotyledons,  when  thrown  off  from  their  parents,  have 
already  the  formed  organs  of  young  plants,  to  which  are 
attached  stores  of  highly  nutritive  matter.  That  is  to  say, 
where  the  young  plant  consists  merely  of  a  centre  of  deve- 
lopment, the  ultimate  growth  is  commonly  insignificant; 
but  where  the  growth  is  to  become  great,  there  exists  to 
start  with,  a  developed  embryo  and  a  stock  of  assimilable 
matter.  Throughout  the  animal  kingdom  this  rela- 

tion is  tolerably  manifest  though  by  no  means  uniform. 
Save  among  classes  that  escape  the  ordinary  requirements  of 
animal  life,  small  germs  or  eggs  do  not  in  most  cases  give 
rise  to  bulky  creatures.  Where  great  bulk  is  to  be  reached, 
the  young  proceeds  from  an  egg  of  considerable  bulk,  or  is 
born  of  considerable  bulk  ready-organized  and  partially 
active.  In  the  class  Fishes,  or  in  such  of  them  as  are  subject 


144:  THE  INDUCTIONS  OP  BIOLOGY. 

io  similar  conditions  of  life,  some  proportion  usually  obtains 
between  the  sizes  of  the  ova  and  the  sizes  of  the  adult  indi- 
viduals; though  in  the  cases  of  the  sturgeon  and  the  tunny 
there  are  exceptions,  probably  determined  by  the  circum- 
stances of  oviposition  and  those  of  juvenile  life.  Eeptiles 
have  eggs  that  are  smaller  in  number,  and  relatively  greater 
in  mass,  than  those  of  fishes;  and  throughout  this  class,  too, 
there  is  a  general  congruity  between  the  bulk  of  the  egg  and 
the  bulk  of  the  adult  creature.  As  a  group,  birds  show  us 
further  limitations  in  the  numbers  of  their  eggs  as  well  as 
further  increase  in  their  relative  sizes;  and  from  the  minute 
eggs  of  the  humming-bird  up  to  the  immense  ones  of  the 
Epiornis,  holding  several  quarts,  we  see  that,  speaking  gene- 
rally, the  greater  the  eggs  the  greater  the  birds.  .  Finally, 
among  mammals  (omitting  the  marsupials)  the  young  are 
born,  not  only  of  comparatively  large  sizes,  but  with  ad- 
vanced organizations;  and  throughout  this  sub-division  of 
the  Vertebrata^  as  throughout  the  others,  there  is  a  mani- 
fest connexion  between  the  sizes  at  birth  and  the  sizes  at 
maturity.  As  having  a  kindred  meaning,  there  must 

finally  be  noted  the  fact  that  the  young  of  these  highest 
animals,  besides  starting  in  life  with  bodies  of  considerable 
sizes,  almost  fully  organized,  are,  during  subsequent  periods 
of  greater  or  less  length,  supplied  with  nutriment — in  birds 
by  feeding  and  in  mammals  by  suckling  and  afterwards  by 
feeding.  So  that  beyond  the  mass  and  organization  directly 
bequeathed,  a  bird  or  mammal  obtains  a  further  large  mass 
at  but  little  cost  to  itself. 

"Were  exhaustive  treatment  of  the  topic  intended,  it  would 
be  needful  to  give  a  paragraph  to  each  of  the  incidental  cir- 
cumstances by  which  growth  may  be  aided  or  restricted: — 
such  facts  as  that  an  entozoon  is  limited  by  the  size  of  the 
creature,  or  even  the  organ,  in  which  it  thrives;  that  an 
epizoon,  though  getting  abundant  nutriment  without  appre- 
ciable exertion,  is  restricted  to  that  small  bulk  at  which  it 
escapes  ready  detection  by  the  animal  it  infests;  that  some- 


GROWTH.  145 

times,  as  in  the  weazel,  smallness  is  a  condition  to  successful 
pursuit  of  the  animals  preyed  upon;  and  that  in  some  cases, 
the  advantage  of  resembling  certain  other  creatures,  and  so 
deceiving  enemies  or  prey,  becomes  an  indirect  cause  of  re- 
stricted size.  But  the  present  purpose  is  simply  to  set  down 
those  most  general  relations  between  growth  and  other  or- 
ganic traits,  which  induction  leads  us  to.  Having  done  this, 
let  us  go  on  to  inquire  whether  these  general  relations  can 
be  deductively  established. 

§  44.  That  there  must  exist  a  certain  dependence  of 
growth  on  organization,  may  be  shown  a  priori.  When  we 
consider  the  phenomena  of  Life,  either  by  themselves  or  in 
their  relations  to  surrounding  phenomena,  we  see  that,  other 
things  equal,  the  larger  the  aggregate  the  greater  is  the  need- 
ful complexity  of  structure. 

In  plants,  even  of  the  highest  type,  there  is  a  compara- 
tively small  mutual  dependence  of  parts:  a  gathered  flower- 
bud  will  unfold  and  flourish  for  days  if  its  stem  be  immersed 
in  water;  and  a  shoot  Cut  off  from  its  parent-tree  and  stuck 
in  the  ground  will  grow.  The  respective  parts  having  vital 
activities  that  are  not  widely  unlike,  it  is  possible  for  great 
bulk  to  be  reached  without  that  structural  complexity 
required  for  combining  the  actions  of  parts.  Even  here, 
however,  we  see  that  for  the  attainment  of  great  bulk  there 
requires  such  a  degree  of  organization  as  shall  co-ordinate 
the  functions  of  roots  and  branches — we  see  that  such  a  size 
as  is  reached  by  trees,  is  not  possible  without  a  vascular 
system  enabling  the  remote  organs  to  utilize  each  other's 
products.  And  we  see  that  such  a  co-existence  of  large 
growth  with  comparatively  low  organization  as  occurs  in 
some  of  the  marine  Algcz,  occurs  where  the  conditions  of 
existence  do  not  necessitate  any  considerable  mutual  depen- 
dence of  parts — where  the  near  approach  of  the  plant  to  its 
medium  in  specific  gravity  precludes  the  need  of  a  well- 
developed  stem,  and  where  all  the  materials  of  growth  being 


.146  THE  INDUCTIONS  OP  BIOLOGY. 

i 

..derived  from  the  water  by  each  portion  of  the  thallus,  there 
requires  no  apparatus  for  transferring  the  crude  food 
materials  from  part  to  part.  Among  animals  which, 

with  but  few  exceptions,  are,  by  the  conditions  of  their 
existence,  required  to  absorb  nutriment  through  one  spe- 
cialized part  of  the  body,  it  is  clear  that  there  must  be  a 
means  whereby  other  parts  of  the  body,  to  be  supported  by 
this  nutriment,  must  have  it  conveyed  to  them.  It  is  clear 
that  for' an  equally  efficient  maintenance  of  their  nutrition,  the 
parts  of  a  large  mass  must  have  a  more  elaborate  propelling 
and  conducting  apparatus;  and  that  in  proportion  as  these 
parts  undergo  greater  waste,  a  yet  higher  development  of 
the  vascular  system  is  necessitated.  Similarly  with  the  pre- 
requisites to  those  mechanical  motions  which  animals  are 
required  to  perform.  The  parts  of  a  mass  cannot  be  made  to 
move,  and  have  their  movements  so  co-ordinated  as  to  pro- 
duce locomotive  and  other  actions,  without  certain  structural 
arrangements;  and,  other  things  equal,  a  given  amount  of 
such  activity  requires  more  involved  structural  arrangements 
in  a  large  mass  than  in  a  small  one.  There  must  at  least  be 
a  co-ordinating  apparatus  presenting  greater  contrasts  in 
its  central  and  peripheral  parts. 

The  qualified  dependence  of  growth  on  organization,  is 
equally  implied  when  we  study  it  in  connexion  with  that 
adjustment  of  inner  to  outer  relations  which  constitutes  Life 
as  phenomenally  known  to  us.  In  plants  this  is  less  striking 
than  in  animals,  because  the  adjustment  of  inner  to  outer 
relations  does  not  involve  conspicuous  motions.  Still,  it  is 
visible  in  the  fact  that  the  condition  on  which  alone  a  plant 
can  grow  to  a  great  size,  is,  that  it  shall,  by  the  development 
of  a  massive  trunk,  present  inner  relations  of  forces  fitted  to 
counterbalance  those  outer  relations  of  forces  which  tend  con- 
tinually, and  others  which  tend  occasionally,  to  overthrow 
it ;  and  this  formation  of  a  core  of  regularly-arranged  woody 
fibres  is  an  advance  in  organization.  Throughout  the 

animal  kingdom  this  connexion  of  phenomena  is  manifest. 


GROWTH.  147 

To  obtain  materials  for  growth;  to  avoid  injuries  which 
interfere  with  growth;  and  to  escape  those  enemies  which 
bring  growth  to  a  sudden  end;  implies  in  the  organism  the 
means  of  fitting  its  movements  to  meet  numerous  external 
co-existences  and  sequences — implies  such  various  structural 
arrangements  as  shall  make  possible  these  variously-adapted 
actions.  It  cannot  be  questioned  that,  everything  else  re- 
maining constant,  a  more  complex  animal,  capable  of  adjust- 
ing its  conduct  to  a  greater  number  of  surrounding  con- 
tingencies, will  be  the  better  able  to  secure  food  and  evade 
damage,  and  so  to  increase  bulk.  And  evidently,  without 
any  qualification,  we  may  say  that  a  large  animal,  living  under 
such  complex  conditions  of  existence  as  everywhere  obtain, 
is  not  possible  without  comparatively  high  organization. 

While,  then,  this  relation  is  traversed  and  obscured  by 
sundry  other  relations,  it  cannot  but  exist.  Deductively  we 
see  that  it  must  be  modified,  as  inductively  we  saw  that  it  is 
modified,  by  the  circumstances  amid  which  each  kind  of  or- 
ganism is  placed,  but  that  it  is  always  a  factor  in  determining 
the  result. 

§45.  That  growth  is,  cceteris  paribus,  dependent  on  the  sup- 
ply of  assimilable  matter,  is  a  proposition  so  continually  illus- 
trated by  special  experience,  as  well  as  so  obvious  from  general 
experience,  that  it  would  scarcely  need  stating,  were  it  not  re- 
quisite to  notice  the  qualifications  with  which  it  must  be  taken. 

The  materials  which  each  organism  requires  for  building 
itself  up,  are  not  of  one  kind  but  of  several  kinds.  As  a 
vehicle  for  transferring  matter  through  their  structures,  all 
organisms  require  water  as  well  as  solid  constituents;  and 
however  abundant  the  solid  constituents  there  can  be  no 
growth  in  the  absence  of  water.  Among  the  solids  supplied, 
there  must  be  a  proportion  ranging  within  certain  limits.  A 
plant  round  which  carbonic  acid,  water,  and  ammonia  exist 
in  the  right  quantities,  may  yet  be  arrested  in  its  growth  by 
a  deficiency  of  potassium.  The  total  absence  of  lime  from  its 


148  THE  INDUCTIONS  OF  BIOLOGY. 

food  may  stop  the  formation  of  a  mammal's  skeleton:  thus 
dwarfing,  if  not  eventually  destroying,  the  mammal;  and 
this  no  matter  what  quantities  of  other  needful  colloids  and 
crystalloids  are  furnished. 

Again,  the  truth  that,  other  things  equal,  growth  varies 
according  to  the  supply  of  nutriment,  has  to  be  qualified  by 
the  condition  that  the  supply  shall  not  exceed  the  ability  to 
appropriate  it.  In  the  vegetal  kingdom,  the  assimilating 
surface  being  external  and  admitting  of  rapid  expansion  by 
the  formation  of  new  roots,  shoots,  and  leaves,  the  effect  of 
this  limitation  is  not  conspicuous.  By  artificially  supplying 
plants  with  those  materials  which  they  have  usually  the  most 
difficulty  in  obtaining,  we  can  greatly  facilitate  their  growth; 
and  so  can  produce  striking  differences  of  size  in  the  same 
species.  Even  here,  however,  the  effect  is  confined  within 
the  limits  of  the  ability  to  appropriate;  since  in  the  absence 
of  that  solar  light  and  heat  by  the  help  of  which  the  chief 
appropriation  is  carried  on,  the  additional  materials  for 
growth  are  useless.  In  the  animal  kingdom  this 

restriction  is  rigorous.  The  absorbent  surface  being,  in  the 
great  majority  of  cases,  internal;  having  a  comparatively 
small  area,  which  cannot  be  greatly  enlarged  without  re- 
construction of  the  whole  body ;  and  being  in  connexion 
with  a  vascular  system  which  also  must  be  re-constructed 
before  any  considerable  increase  of  nutriment  can  be  made 
available;  it  is  clear  that  beyond  a  certain  point,  very  soon 
reached,  increase  of  nutriment  will  not  cause  increase  of 
growth.  On  the  contrary,  if  the  quantity  of  food  taken  in  is 
greatly  beyond  the  digestive  and  absorbent  power,  the  excess, 
becoming  an  obstacle  to  the  regular  working  of  the  organism, 
may  retard  growth  rather  than  advance  it. 

While  then  it  is  certain,  a  priori,  that  there  cannot  be 
growth  in  the  absence  of  such  substances  as  those  of  which 
an  organism  consists ;  and  while  it  is  equally  certain  that  the 
amount  of  growth  must  primarily  be  governed  by  the  supply 
of  these  substances;  it  is  not  less  certain  that  extra  supply 


GROWTH.  149 

will  not  produce  extra  growth,  beyond  a  point  very  soon 
reached.  Deduction  shows  to  be  necessary,  as  induction 
makes  familiar,  the  truths  that  the  value  of  food  for  purposes 
of  growth  depends  not  on  the  quantity  of  the  various  organi- 
zable  materials  it  contains,  but  on  the  quantity  of  the  mate- 
rial most  needed ;  that  given  a  right  proportion  of  materials, 
the  pre-existing  structure  of  the  organism  limits  their 
availability;  and  that  the  higher  the  structure,  the  sooner 
is  this  limit  reached. 

§  46.  But  why  should  the  growth  of  every  organism  be 
finally  arrested?  Though  the  rate  of  increase  may,  in  each 
case,  be  necessarily  restricted  within  a  narrow  range  of  varia- 
tion— though  the  increment  that  is  possible  in  a  given  time, 
cannot  exceed  a  certain  amount;  yet  why  should  the  incre- 
ments decrease  and  finally  become  insensible?  Why  should 
not  all  organisms,  when  supplied  with  sufficient  materials, 
continue  to  grow  as  long  as  they  live?  To  find  an  answer  to 
this  question  we  must  revert  to  the  nature  and  functions  of 
organic  matter. 

In  the  first  three  chapters  of  Part  I,  it  was  shown  that 
plants  and  animals  mainly  consist  of  substances  in  states  of 
unstable  equilibrium — substances  which  have  been  raised  to 
this  unstable  equilibrium  by  the  expenditure  of  the  forces  we 
know  as  solar  radiations,  and  which  give  out  these  forces  in 
other  forms  on  falling  into  states  of  stable  equilibrium. 
Leaving  out  the  water,  which  serves  as  a  vehicle  for  these 
materials  and  a  medium  for  their  changes;  and  excluding 
those  mineral  matters  that  play  either  passive  or  subsidiary 
parts ;  organisms  are  built  up  of  compounds  which  are  stores 
of  force.  Thus  complex  colloids  and  crystalloids  which,  as 
united  together,  form  organized  bodies,  are  the  same  colloids 
and  crystalloids  which  give  out,  on  their  decomposition,  the 
forces  expended  by  organized  bodies.  Thus  these 

nitrogenous  and  carbonaceous  substances,  being  at  once 
the  materials  for  organic  growth  and  the  sources  of  organic 


150  THE  INDUCTIONS  OF  BIOLOGY. 

energy,  it  results  that  as  much  of  them  as  is  used  up  for  the 
genesis  of  energy  is  taken  away  from  the  means  of  growth, 
and  as  much  as  is  economized  by  diminishing  the  genesis  of 
energy,  is  available  for  growth.  Given  that  limited  quantity 
of  nutritive  matter  which  the  pre-existing  structure  of  an 
organism  enables  it  to  absorb;  and  it  is  a  necessary  corollary 
from  the  persistence  of  force,  that  the  matter  accumulated  as 
growth  cannot  exceed  that  surplus  which  remains  unde- 
composed  after  the  production  of  the  required  amounts  of 
sensible  and  insensible  motion.  This,  which  would 

be  rigorously  true  under  all  conditions  if  exactly  the  same 
substances  were  used  in  exactly  the  same  proportions  for  the 
production  of  force  and  for  the  formation  of  tissue,  requires, 
however,  to  be  taken  with  the  qualification  that  some  of  the 
force-evolving  substances  are  not  constituents  of  tissue;  and 
that  thus  there  may  be  a  genesis  of  force  which  is  not  at  the 
expense  of  potential  growth.  But  since  organisms  (or  at 
least  animal  organisms,  with  which  we  are  here  chiefly 
concerned)  have  a  certain  power  of  selective  absorption, 
which,  partially  in  an  individual  and  more  completely  in  a 
race,  adapts  the  proportions  of  the  substances  absorbed  to  the 
needs  of  the  system;  then  if  a  certain  habitual  expenditure 
of  force  leads  to  a  certain  habitual  absorption  of  force- 
evolving  matters  that  are  not  available  for  growth;  and  if, 
were  there  less  need  for  such  matters,  the  ability  to  absorb 
matters  available  for  growth  would  be  increased  to  an  equi- 
valent extent ;  it  follows  that  the  antagonism  described  does, 
in  the  long  run,  hold  even  without  this  qualification.  Hence, 
growth  is  substantially  equivalent  to  the  absorbed  nutriment, 
minus  the  nutriment  used  up  in  action. 

This,  however,  is  no  answer  to  the  question — why  has 
individual  growth  a  limit? — why  do  the  increments  of 
growth  bear  decreasing  ratios  to  the  mass  and  finally  come 
to  an  end  ?  The  question  is  involved.  There  are  more  causes 
than  one  why  the  excess  of  absorbed  nutriment  over  ex- 
pended nutriment  must,  other  things  equal,  become  less  as 


GROWTH.  151 

\ 

the  size  of  the  animal  becomes  greater.  In  similarly- 

shaped  bodies  the  masses,  and  therefore  the  weights,  vary  as 
the  cubes  of  the  dimensions;  whereas  the  powers  of  bearing 
the  stresses  imposed  by  the  weights  vary  as  the  squares  of 
the  dimensions.  Suppose  a  creature  which  a  year  ago  was 
one  foot  high,  has  now  become  two  feet  high,  while  it  is 
unchanged  in  proportions  and  structure;  what  are  the  neces- 
sary concomitant  changes?  It  is  eight  times  as  heavy;  that 
is  to  say,  it  has  to  resist  eight  times  the  strain  which  gravi- 
tation puts  upon  certain  of  its  parts;  and  when  there 
occurs  sudden  arrest  of  motion  or  sudden  genesis  of  motion, 
eight  times  the  strain  is  put  upon  the  muscles  employed. 
Meanwhile  the  muscles  and  bones  have  severally  increased 
their  abilities  to  bear  strains  in  proportion  to  the  areas  of 
their  transverse  sections,  and  hence  have  severally  only  four 
times  the  tenacity  they  had.  This'  relative  decrease  in  the 
power  of  bearing  stress  does  not  imply  a  relative  decrease  in 
the  power  of  generating  energy  and  moving  the  body ;  for  in 
the  case  supposed  the  muscles  have  not  only  increased  four 
times  in  their  transverse  sections  but  have  become  twice  as 
long,  and  will  therefore  generate  an  amount  of  energy  propor- 
tionate to  their  bulk.  The  implication  is  simply  that  each 
muscle  has  only  half  the  power  to  withstand  those  shocks  and 
strains  which  the  creature's  movements  entail ;  and  that  con- 
sequently the  creature  must  be  either  less  able  to  bear  these, 
or  must  have  muscles  and  bones  having  relatively  greater 
transverse  dimensions:  the  result  being  that  greater  cost  of 
nutrition  is  inevitably  caused  and  therefore  a  correlative 
tendency  to  limit  growth.  This  necessity  will  be  seen  still 
more  clearly  if  we  leave  out  the  motor  apparatus,  and  con- 
sider only  the  forces  required  and  the  means  of  supplying 
them.  For  since,  in  similar  bodies,  the  areas  vary  as  the 
squares  of  the  dimensions,  and  the  masses  vary  as  the  cubes ; 
it  follows  that  the  absorbing  surface  has  become  four  times 
as  great,  while  the  weight  to  be  moved  by  the  matter  ab- 
sorbed has  become  eight  times  as  great.  If  then,  a  year 


152  THE  INDUCTIONS  OP   BIOLOGY. 

ago,  the  absorbing  surface  could  take  up  twice  as  much 
nutriment  as  was  needed  for  expenditure,  thus  leaving  one- 
half  for  growth,  it  is  now  able  only  just  to  meet  expenditure, 
and  can  provide  nothing  for  growth.  However  great  the 
excess  of  assimilation  over  waste  may  be  during  the  early 
life  of  an  active  organism,  we  see  that  because  a  series  of 
numbers  increasing  as  the  cubes,  overtakes  a  series  increasing 
as  the  squares,  even  though  starting  from  a  much  smaller 
number,  there  must  be  reached,  if  the  organism  lives  long 
enough,  a  point  at  which  the  surplus  assimilation  is  brought 
down  to  nothing — a  point  at  which  expenditure  balances 
nutrition — a  state  of  moving  equilibrium.  The  only  way  in 
which  the  difficulty  can  be  met  is  by  gradual  re-organization 
of  the  alimentary  system ;  and,  in  the  first  place,  this  entails 
direct  cost  upon  the  organism,  and,  in  the  second  place,  indi- 
rect cost  from  the  carrying  of  greater  weight:  both  tending 
towards  limitation.  There  are  two  other  varying 

relations  between  degrees  of  growth  and  amounts  of  expended 
force;  one  of  which  conspires  with  the  last,  while  the  other 
conflicts  with  it.  Consider,  in  the  first  place,  the  cost  at 
which  nutriment  is  distributed  through  the  body  and  effete 
matters  removed  from  it.  Each  increment  of  growth  being 
added  at  the  periphery  of  the  organism,  the  force  expended 
in  the  transfer  of  matter  must  increase  in  a  rapid  progression 
— a  progression  more  rapid  than  that  of  the  mass.  But  as 
the  dynamic  expense  of  distribution  is  small  compared  with 
the  dynamic  value  of  the  materials  distributed,  this  item  in 
the  calculation  is  unimportant.  Now  consider,  in  the  second 
place,  the  changing  proportion  between  production  and  loss 
of  heat.  In  similar  organisms  the  quantities  of  heat  gene- 
rated by  similar  actions  going  on  throughout  their  substance, 
must  increase  as  the  masses,  or  as  the  cubes  of  the  dimen- 
sions. Meanwhile,  the  surfaces  from  which  loss  of  heat 
takes  place,  increase  only  as  the  squares  of  the  dimensions. 
Though  the  loss  of  heat  does  not  therefore  increase  only  as 
the  squares  of  the  dimensions,  it  certainly  increases  at  a 


GROWTH.  153 

smaller  rate  than  the  cubes.  And  to  the  extent  that  aug- 
mentation of  mass  results  in  a  greater  retention  of  heat,  it 
effects  an  economization  of  force.  This  advantage  is  not, 
however,  so  important  as  at  first  appears.  Organic  heat  is  a 
concomitant  of  organic  action,  and  is  so  abundantly  produced 
during  action  that  the  loss  of  it  is  then  usually  of  no  conse- 
quence :  indeed  the  loss  is  often  not  rapid  enough  to  keep  the 
supply  from  rising  to  an  inconvenient  excess.  It  is  chiefly 
in  respect  of  that  maintenance  of  heat  which  is  needful 
during  quiescence,  that  large  organisms  have  an  advantage 
over  small  ones  in  this  relatively  diminished  loss.  Thus 
these  two  subsidiary  relations  between  degrees  of  growth  and 
amounts  of  expended  force,  being  in  antagonism,  we  may 
conclude  that  their  differential  result  does  not  greatly  modify 
the  result  of  the  chief  relation. 

Comparisons  of  these  deductions  with  the  facts  appear  in 
some  cases  to  verify  them  and  in  other  cases  not  to  do  so. 
Throughout  the  vegetal  kingdom,  there  are  no  distinct  limits 
to  growth  except  those  which  death  entails.  Passing  over  a 
large  proportion  of  plants  which  never  exceed  a  comparatively 
small  size,  because  they  wholly  or  partially  die  down  at  the 
end  of  the  year,  and  looking  only  at  trees  that  annually  send 
forth  new  shoots,  even  when  their  trunks  are  hollowed  by 
decay;  we  may  ask — How  does  growth  happen  here  to  be 
unlimited?  The  answer  is,  that  plants  are  only  accumula- 
tors :  they  are  in  no  very  appreciable  degree  expenders.  As 
they  do  not  undergo  waste  there  is  no  reason  why  their 
growth  should  be  arrested  by  the  equilibration  of  assimilation 
and  waste.  Again,  among  animals  there  are  sufficient 

reasons  why  the  correspondence  cannot  be  more  than  approxi- 
mate. Besides  the  fact  above  noted,  that  there  are  other 
varying  relations  which  complicate  the  chief  one.  We  must 
bear  in  mind  that  the  bodies  compared  are  not  truly  similar : 
the  proportions  of  trunk  to  limbs  and  trunk  to  head,  vary 
considerably.  The  comparison  is  still  more  seriously  vitiated 
by  the  inconstant  ratio  between  the  constituents  of  which 


154  THE  INDUCTIONS  OP   BIOLOGY. 

the  body  is  composed.  In  the  flesh  of  adult  mammalia,  water 
forms  from  68  to  71  per  cent.,  organic  substance  from  24  to 
28  per  cent.,  'and  inorganic  substance  from  3  to  5  per  cent. ; 
whereas  in  the  foetal  state,  the  water  amounts  to  87  per  cent., 
and  the  solid  organic  constituents  to  only  11  per  cent.  Clearly 
this  change  from  a  state  in  which  the  force-evolving  matter 
forms  one-tenth  of  the  whole,  to  a  state  in  which  it  forms  two 
and  a  half  tenths,  must  greatly  interfere  with  the  parallelism 
between  the  actual  and  the  theoretical  progression.  Yet 

another  difficulty  may  come  under  notice.  The  crocodile  is 
said  to  grow  as  long  as  it  lives;  and  there  appears  reason  to 
think  that  some  predaceous  fishes,  such  as  the  pike,  do  the 
same.  That  these  animals  of  comparatively  high  organization 
have  no  definite  limits  of  growth,  is,  however,  an  exceptional 
fact  due  to  the  exceptional  non-fulfilment  of  those  conditions 
which  entail  limitation.  What  kind  of  life  does  a  crocodile 
lead?  It  is  a  cold-blooded,  or  almost  cold-blooded,  creature; 
that  is,  it  expends  very  little  for  the  maintenance  of  heat. 
It  is  habitually  inert:  not  usually  chasing  prey  but  lying  in 
wait  for  it;  and  undergoes  considerable  exertion  only  during 
its  occasional  brief  contests  with  prey.  Such  other  exertion 
as  is,  at  intervals,  needful  for  moving  from  place  to  place,  is 
rendered  small  by  the  small  difference  between  the  animal's 
specific  gravity  and  that  of  water.  Thus  the  crocodile  ex- 
pends in  muscular  action  an  amount  of  force  that  is  insignifi- 
cant compared  with  the  force  commonly  expended  by  land- 
animals.  Hence  its  habitual  assimilation  is  diminished  much 
less  than  usual  by  habitual  waste;  and  beginning  with  an 
excessive  disproportion  between  the  two,  it  is  quite  possible 
for  the  one  never  quite  to  lose  its  advance  over  the  other 
while  life  continues.  On  looking  closer  into  such  cases  as 
this  and  that  of  the  pike,  which  is  similarly  cold-blooded, 
similarly  lies  in  wait,  and  is  similarly  able  to  obtain  larger 
and  larger  kinds  of  prey  as  it  increases  in  size;  we  discover 
a  further  reason  for  this  absence  of  a  definite  limit.  To  over- 
come gravitative  force  the  creature  has  not  to  expend  a 


GROWTH.  155 

muscular  power  that  is  large  at  the  outset,  and  increases  as 
the  cubes  of  its  dimensions:  its  dense  medium  supports  it. 
The  exceptional  continuance  of  growth  observed  in  creatures 
so  circumstanced,  is  therefore  perfectly  explicable. 

§  4Ga.  If  we  go  back  upon  the  conclusions  set  forth  in  the 
preceding  section,  we  find  that  from  some  of  them  may  be 
drawn  instructive  corollaries  respecting  the  limiting  sizes  of 
creatures  inhabiting  different  media.  More  especially  I  refer 
to  those  varying  proportions  between  mass  and  stress  from 
which,  as  we  have  seen,  there  results,  along  with  increasing 
size,  a  diminishing  power  of  mechanical  self-support :  a  rela- 
tion illustrated  in  its  simplest  form  by  the  contrast  between 
a  dew-drop,  which  can  retain  its  spheroidal  form,  and  the 
spread-out  mass  of  water  which  results  when  many  dew-drops 
run  together.  The  largest  bird  that  flies  (the  argument 
excludes  birds  which  do  not  fly)  is  the  Condor,  which  reaches 
a  weight  of  from  30  to  40  Ibs.  Why  does  there  not  exist  a  bird 
of  the  size  of  an  elephant?  Supposing  its  habits  to  be 
carnivorous,  it  would  have  many  advantages  in  obtaining 
prey:  mammals  would  be  at  its  mercy.  Evidently  the 
reason  is  one  which  has  been  pointed  out — the  reason  that 
while  the  weight  to  be  raised  and  kept  in  the  air  by  a  bird 
increases  as  the  cubes  of  its  dimensions,  the  ability  of  its 
bones  and  muscles  to  resist  the  strains  which  flight  neces- 
sitates, increases  only  as  the  squares  of  the  dimensions. 
Though,  could  the  muscles  withstand  any  tensile  strain  they 
were  subject  to,  the  power  like  the  weight  might  increase 
with  the  cubes,  yet  since  the  texture  of  muscle  is  such  that 
beyond  a  certain  strain  it  tears,  it  results  that  there  is  soon 
reached  a  size  at  which  flight  becomes  impossible :  the  struc- 
tures must  give  way.  In  a  preceding  paragraph  the  limit  to 
the  size  of  flying  creatures  was  ascribed  to  the  greater 
physiological  cost  of  the  energy  required;  but  it  seems 
probable  that  the  mechanical  obstacle  here  pointed  out  has 
a  larger  share  in  determining  the  limit. 


156  THE  INDUCTIONS  OP  BIOLOGY. 

In  a  kindred  manner  there  results  a  limitation  of  growth 
in  a  land-animal,  which  does  not  exist  for  an  animal  living 
in  the  water.  If,  after  comparing  the  agile  movements  of 
a  dog  with  those  of  a  cow,  the  great  weight  of  which  ob- 
viously prevents  agility;  or  if,  after  observing  the  swaying 
flesh  of  an  elephant  as  it  walks  along,  we  consider  what 
would  happen  could  there  be  formed  a  land-animal  equal 
in  mass  to  the  whale  (the  long  Dinosaurs  were  not  propor- 
tionately massive)  it  needs  no  argument  to  show  that  such 
a  creature  could  not  stand,  much  less  move  about.  But 
in  the  water  the  strain  put  upon  its  structures  by  the  weights 
of  its  various  parts  is  almost  if  not  quite  taken  away.  Prob- 
ably limitation  in  the  quantity  of  food  obtainable  becomes 
now  the  chief,  if  not  the  sole,  restraint. 

And  here  we  may  note,  before  leaving  the  topic,  something 
like  a  converse  influence  which  comes  into  play  among 
creatures  inhabiting  the  water.  Up  to  the  point  at  which 
muscles  tear  from  over-strain,  larger  and  smaller  creatures 
otherwise  alike,  remain  upon  a  par  in  respect  of  the  relative 
amounts  of  energy  they  can  evolve.  Had  they  to  encounter 
no  resistance  from  their  medium,  the  implication  would  be 
that  neither  would  have  an  advantage  over  the  other  in 
respect  of  speed.  But  resistance  of  the  medium  comes  into 
play;  and  this,  other  things  equal,  gives  to  the  larger 
creature  an  advantage.  It  has  been  found,  experimentally, 
that  the  forces  to  be  overcome  by  vessels  moving  through 
the  water,  built  as  they  are  with  immersed  hinder  parts 
which  taper  as  fish  taper,  are  mainly  due  to  what  is  called 
"  skin-friction."  Now  in  two  fish  unlike  in  size  but  other- 
wise similar  skin-friction  bears  to  the  energy  that  can  be 
generated,  a  smaller  proportion  in  the  larger  than  in  the 
smaller;  and  the  larger  can  therefore  acquire  a  greater 
velocity.  Hence  the  reason  why  large  fish,  such  as  the 
shark,  become  possible.  In  a  habitat  where  there  is  no  am- 
bush (save  in  exceptional  cases  like  that  of  the  LopJiius  or 
Angler)  everything  depends  on  speed;  and  if,  other  things 


GROWTH.  15f 

equal,  a  larger  fish  had  no  mechanical  advantage  over  a 
smaller,  a  larger  fish  could  not  exist — could  not  catch  the 
requisite  amount  of  prey. 

§47.  Obviously  this  antagonism  between  accumulation  and 
expenditure,  must  be  a  leading  cause  of  the  contrasts  in  size 
between  allied  organisms  that  are  in  many  respects  similarly 
conditioned.  The  life  followed  by  each  kind  of  animal  is 
one  involving  a  certain  average  amount  of  exertion  for  the 
obtainment  of  a  given  amount  of  nutriment — an  exertion, 
part  of  which  goes  to  the  gathering  or  catching  of  food,  part 
to  the  tearing  and  mastication  of  it,  and  part  to  the  after- 
processes  requisite  for  separating  the  nutritive  molecules — an 
exertion  which  therefore  varies  according  as  the  food  is 
abundant  or  scarce,  fixed  or  moving,  according  as  it  is  me- 
chanically easy  or  difficult  to  deal  with  when  secured,  and 
according  as  it  is,  or  is  not,  readily  soluble.  Hence,  while 
among  animals  of  the  same  species  having  the  same  mode  of 
life,  there  will  be  a  tolerably  constant  ratio  between  accumu- 
lation and  expenditure,  and  therefore  a  tolerably  constant 
limit  of  growth,  there  is  every  reason  to  expect  that  different 
species,  following  different  modes  of  life,  will  have  unlike 
ratios  between  accumulation  and  expenditure,  and  therefore 
unlike  limits  of  growth. 

Though  the  facts  as  inductively  established,  show  a  general 
harmony  with  this  deduction,  we  cannot  usually  trace  it  in 
any  specific  way ;  since  the  conflicting  and  conspiring  factors 
which  affect  growth  are  so  numerous. 

§  48.  One  of  the  chief  causes,  if  not  the  chief  cause,  of 
the  differences  between  the  sizes  of  organisms,  has  yet  to  be 
considered.  We  are  introduced  to  it  by  pushing  the  above 
inquiry  a  little  further.  Small  animals  have  been  shown  to 
possess  an  advantage  over  large  ones  in  the  greater  ratio 
which,  other  things  equal,  assimilation  bears  to  expenditure; 
and  we  have  seen  that  hence  small  animals  in  becoming  large 


158  THE   INDUCTIONS   OF   BIOLOGY. 

ones,  gradually  lose  that  surplus  of  assimilative  power  which 
they  had,  and  eventually  cannot  assimilate  more  than  is  re- 
quired to  balance  waste.  But  how  come  these  animals  while 
young  and  small  to  have  surplus  assimilative  powers?  Have 
all  animals  equal  surpluses  of  assimilative  powers?  And 
if  not,  how  far  do  differences  between  the  surpluses  de- 
termine differences  between  the  limits  of  growth  ?  We 
shall  find,  in  the  answers  to  these  questions,  the  interpretation 
of  many  marked  contrasts  in  growth  that  are  not  due  to  any 
of  the  causes  above  assigned.  For  example,  an  ox  immensely 
exceeds  a  sheep  in  mass.  Yet  the  two  live  from  generation 
to  generation  in  the  same  fields,  eat  the  same  grass,  obtain 
these  aliments  with  the  same  small  expenditure  of  energy, 
and  differ  scarcely  at  all  in  their  degrees  of  organization. 
Whence  arises,  then,  their  striking  unlikeness  of  bulk? 

We  noted  when  studying  the  phenomena  of  growth  in- 
ductively, that  organisms  of  the  larger  and  higher  types  com- 
mence their  separate  existences  as  masses  of  organic  matter 
having  tolerable  magnitudes.  Speaking  generally,  we  saw 
that  throughout  each  organic  sub-kingdom  the  acquirement 
of  great  bulk  occurs  only  where  the  incipient  bulk  and  or- 
ganization are  considerable;  and  that  they  are  the  more  con- 
siderable in  proportion  to  the  complexity  of  the  life  which 
the  organism  is  to  lead. 

The  deductive  interpretation  of  this  induction  may  best 
be  commenced  by  an  analogy.  A  street  orange-vendor 
makes  but  a  trifling  profit  on  each  transaction ;  and  unless 
more  than  ordinarily  fortunate,  he  is  unable  to  realize 
during  the  day  a  larger  amount  than  will  meet  his  wants; 
leaving  him  to  start  on  the  morrow  in  the  same  condition 
as  before.  The  trade  of  the  huxter  in  ounces  of  tea  and 
half-pounds  of  sugar,  is  one  similarly  entailing  much  labour 
for  small  returns.  Beginning  with  a  capital  of  a  few 
pounds,  he  cannot  have  a  shop  large  enough,  or  goods 
sufficiently  abundant  and  various,  to  permit  an  extensive 
business.  He  must  be  content  with  the  half-pence  and  pence 


GROWTH.  159 

which  he  makes  by  little  sales  to  poor  people;  and  if,  avoid- 
ing bad  debts,  he  is  able  by  strict  economy  to  accumulate 
anything,  it  can  be  but  a  trifle.  A  large  retail  trader  is 
obliged  to  lay  out  much  money  in  fitting  up  an  adequate 
establishment;  he  must  invest  a  still  greater  sum  in  stock; 
and  he  must  have  a  further  floating  capital  to  meet  the 
charges  that  fall  due  before  his  returns  come  in.  Setting 
out,  however,  with  means  enough  for  these  purposes,  he  is 
able  to  make  many  and  large  sales;  and  so  to  get  greater 
and  more  numerous  increments  of  profit.  Similarly,  to  get 
returns  in  thousands  merchants  and  manufacturers  must 
make  their  investments  in  tens  of  thousands.  In  brief,  the 
rate  at  whi^h  a  man's  wealth  accumulates  is  measured  by 
the  surplus  of  income  over  expenditure;  and  this,  save  in 
exceptionably  favourable  cases,  is  determined  by  the  capital 
with  which  he  begins  business.  Xow  applying  the 

analogy,  we  may  trace  in  the  transactions  of  an  organism, 
the  same  three  ultimate  elements.  There  is  the  expenditure 
required  for  the  obtainment  and  digestion  of. food;  there  is 
the  gross  return  in  the  shape  of  nutriment  assimilated  or  fit 
for  assimilation;  and  there  is  the  difference  between  this 
gross  return  of  nutriment  and  the  nutriment  that  was  used 
up  in  the  labour  of  securing  it — a  difference  which  may  be  a 
profit  or  a  loss.  Clearly,  however,  a  surplus  implies  that  the 
force  expended  is  less  than  the  force  latent  in  the  assimilated 
food.  Clearly,  too,  the  increment  of  growth  is  limited  to 
the  amount  of  this  surplus  of  income  over  expenditure;  so 
that  large  growth  implies  both  that  the  excess  of  nutrition 
over  waste  shall  be  relatively  considerable,  and  that  the  waste 
and  nutrition  shall  be  on  extensive  scales.  And  clearly, 
the  ability  of  an  organism  to  expend  largely  and  assimilate 
largely,  so  as  to  make  a  large  surplus,  presupposes  a  large 
physiological  capital  in  the  shape  of  organic  matter  more  or 
less  developed  in  its  structural  arrangements. 

Throughout  the  vegetal  kingdom,  the  illustrations  of  this 


160  THE   INDUCTIONS  OF  BIOLOGY. 

truth  are  not  conspicuous  and  regular:  the  obvious  reason 
being  that  since  plants  are  accumulators  and  in  so  small  a 
degree  expenders,  the  premises  of  the  above  argument  are 
but  very  partially  fulfilled.  The  food  of  plants  (excepting 
Fungi  and  certain  parasites)  being  in  great  measure  the 
same  for  all,  and  bathing  all  so  that  it  can  be  absorbed  with- 
out effort,  their  vital  processes  result  almost  entirely  in  profit. 
Once  fairly  rooted  in  a  fit  place,  a  plant  may  thus  from  the 
outset  add  a  very  large  proportion  of  its  entire  returns  to 
capital;  and  may  soon  be  able  to  carry  on  its  processes  on  a 
large  scale,  though  it  does  not  at  first  do  so.  When,  however, 
plants  are  expenders,  namely,  during  their  germination  and 
first  stages  of  growth,  their  degrees  of  growth  ar«  determined 
by  their  amounts  of  vital  capital.  It  is  because  the  young 
tree  commences  life  with  a  ready-formed  embryo  and  store 
of  food  sufficient  to  last  for  some  time,  that  it  is  enabled 
to  strike  root  and  lift  its  head  above  the  surrounding 
herbage.  Throughout  the  animal  kingdom,  however, 

the  necessity  of  this  relation  is  everywhere  obvious.  The 
small  carnivore  preying  on  small  herbivores,  can  increase  in 
size  only  by  small  increments :  its  organization  unfitting  it  to 
digest  larger  creatures,  even  if  it  can  kill  them,  it  cannot 
profit  by  amounts  of  nutriment  exceeding  a  narrow  limit; 
and  its  possible  increments  of  growth  being  small  to  set  out 
with,  and  rapidly  decreasing,  must  come  to  an  end  before 
any  considerable  size  is  attained.  Manifestly  the  young  lion, 
born  of  tolerable  bulk,  suckled  until  much  bigger,  and  fed 
until  half-grown,  is  enabled  by  the  power  and  organization 
which  he  thus  gets  gratis,  to  catch  and  kill  animals  big 
enough  to  give  him  the  supply  of  nutriment  needed  to  meet 
his  large  expenditure  and  yet  leave  a  large  surplus  for 
growth.  Thus,  then,  is  explained  the  above-named  contrast 
between  the  ox  and  the  sheep.  A  calf  and  a  lamb  com- 
mence their  physiological  transactions  on  widely  different 
scales;  their  first  increments  of  growth  are  similarly  con- 


GROWTH.  161 

trasted  in  their  amounts;   and  the  two  diminishing  series  of 
such  increments  end  at  similarly-contrasted  limits. 

§  49.  Such  are  the  several  conditions  by  which  the  phe- 
nomena of  growth  are  determined.  Conspiring  and  conflict- 
ing in  endless  unlike  ways  and  degrees,  they  in  every  case 
qualify  more  or  less  differently  each  other's  effects.  Hence  it 
happens  that  we  are  obliged  to  state  each  generalization  as  true 
on  the  average,  or  to  make  the  proviso — other  things  equal. 

Understood  in  this  qualified  form,  our  conclusions  are 
these.  First,  that  growth  being  an  integration  with  the 
organism  of  such  environing  matters  as  are  of  like  natures 
with  the  matters  composing  the  organism,  its  growth  is  de- 
pendent on  the  available  supply  of  them.  Second,  that  the 
available  supply  of  assimilable  matter  being  the  same,  and 
other  conditions  not  dissimilar,  the  degree  of  growth  varies 
according  to  the  surplus  of  nutrition  over  expenditure — a 
generalization  which  is  illustrated  in  some  of  the  broader 
contrasts  between  different  divisions  of  organisms.  Third, 
that  in  the  same  organism  the  surplus  of  nutrition  over 
expenditure  differs  at  different  stages;  and  that  growth  is 
unlimited  or  has  a  definite  limit,  according  as  the  surplus 
does  or  does  not  rapidly  decrease.  This  proposition  we  found 
exemplified  by  the  almost  unceasing  growth  of  organisms 
that  expend  relatively  little  energy;  and  by  the  definitely 
limited  growth  of  organisms  that  expend  much  energy. 
Fourth,  that  among  organisms  which  are  large  expenders  of 
force,  the  size  ultimately  attained  is,  other  things  equal, 
determined  by  the  initial  size :  in  proof  of  which  conclusion 
we  have  abundant  facts,  as  well  as  the  a  priori  necessity 
that  the  sum-totals  of  analogous  diminishing  series,  must 
depend  upon  the  amounts  of  their  initial  terms.  Fifth,  that 
where  the  likeness  of  other  circumstances  permits  a  com- 
parison, the  possible  extent  of  growth  depends  on  the  degree 
of  organization ;  an  inference  testified  to  by  the  larger  forms 
among  the  various  divisions  and  sub-divisions  of  organisms. 


CHAPTER  II. 

DEVELOPMENT.* 

§  50.  CERTAIN  general  aspects  of  Development  may  be 
studied  apart  from  any  examination  of  internal  structures. 
These  fundamental  contrasts  between  the  modes  of  arrange- 
ment of  parts,  originating,  as  they  do,  the  leading  external 
distinctions  among  the  various  forms  of  organization,  will  be 
best  dealt  with  at  the  outset.  If  all  organisms  have  arisen 
by  Evolution,  it  is  of  course  not  to  be  expected  that  such 
several  modes  of  development  can  be  absolutely  demarcated: 
we  are  sure  to  find  them  united  by  transitional  modes.  But 
premising  that  a  classification  of  modes  can  but  approximately 
represent  the  facts,  we  shall  find  our  general  conceptions  of 
Development  aided  by  one. 

Development  is  primarily  central.  All  organic  forms  of 
which  the  entire  history  is  known,  set  out  with  a  symmetri- 
cal arrangement  of  parts  round  a  centre.  In  organisms  of 
the  lowest  grade  no  other  mode  of  arrangement  is  ever 
definitely  established;  and  in  the  highest  organisms  central 
development,  though  subordinate  to  another  mode  of  develop- 
ment, continues  to  be  habitually  shown  in  the  changes  of 
minute  structure.  Let  us  glance  at  these  propositions  in  the 

*  In  ordinary  speech  Development  is  often  used  as  synonymous  with 
Growth.  It  hence  seems  needful  to  say  that  Development  as  here  and  here- 
after used,  means  increase  of  structure  and  not  increase  of  bulk.  It  may  be 
added  that  the  word  Evolution,  comprehending  growth  as  well  as  Develop- 
ment,  is  to  be  reserved  for  occasions  when  both  are  implied. 
162 


DEVELOPMENT.  163 

concrete.  Practically  every  plant  and  every  animal 

in  its  earliest  stage  is  a  portion  of  protoplasm,  in  the  great 
majority  of  cases  approximately  spherical  but  sometimes  elong- 
ated, containing  a  rounded  body  consisting  of  specially  modi- 
fied protoplasm,  which  is  called  a  nucleus ;  and  the  first  changes 
that  occur  in  the  germ  thus  constituted,  are  changes  that  take 
place  in  this  nucleus,  followed  by  changes  round  the  centres 
produced  by  division  of  this  original  centre.  From  this  type  of 
structure,  the  simplest  organisms  do  not  depart ;  or  depart  in 
no  definite  or  conspicuous  ways.  Among  plants,  many  of  the 
simplest  Algce  and  Fungi  permanently  maintain  such  a  central 
distribution;  while  among  animals  it  is  permanently  main- 
tained by  creatures  like  the  Gregarina,  and  in  a  different  man- 
ner by  the  Amoeba,  Actinophrys,  and  their  allies :  the  irregu- 
larities which  are  many  and  great  do  not  destroy  this  general 
relation  of  parts.  In  larger  organisms,  made  up  chiefly  of 
units  that  are  analogous  to  these  simplest  organisms,  the  for- 
mation of  units  ever  continues  to  take  place  round  nuclei; 
though  usually  the  nuclei  soon  cease  to  be  centrally  placed. 

Central  development  may  be  distinguished  into  unicentral 
and  muHicentral ;  according  as  the  product  of  the  original 
germ  develops  more  or  less  symmetrically  round  one  centre, 
or  develops  without  subordination  to  one  centre — develops, 
that  is,  in  subordination  to  many  centres.  Unicentral 

development,  as  displayed  not  in  the  formation  of  single 
cells  but  in  the  formation  of  aggregates,  is  not  common.  The 
animal  kingdom  shows  it  .only  in  some  of  the  small  group  of 
colonial  Eadiolaria.  It  is  feebly  represented  in  the  vegetal 
kingdom  by  a  few  members  of  the  Volvocineoe.  On  the 

other  hand,  multicentral  development,  or  development  round 
insubordinate  centres,  is  variously  exemplified  in  both  divi- 
sions of  the  organic  world.  It  is  exemplified  in  two  distinct 
ways,  according  as  the  insubordination  among  the  centres  of 
development  is  partial  or  total.  We  may  most  conveniently 
consider  it  under  the  heads  hence  arising. 

Total  insubordination  among  the  centres  of  development, 


164  THE  INDUCTIONS  OP  BIOLOGY. 

is  shown  where  the  units  or  cells,  as  fast  as  they  are  seve- 
rally formed,  part  company  and  lead  independent  lives. 
This,  in  the  vegetal  kingdom,  habitually  occurs  among  the 
Protopliyta,  and  in  the  animal  kingdom,  among  the  Proto- 
zoa. Partial  insubordination  is  seen  in  those  somewhat 
advanced  organisms,  that  consist  of  units  which,  though  they 
have  not  separated,  have  so  little  mutual  dependence  that 
the  aggregate  they  form  is  irregular.  Among  plants,  the 
Thallophytes  very  generally  exemplify  this  mode  of  de- 
velopment. Lichens,  spreading  with  flat  or  corrugated  edges 
in  this  or  that  direction  as  the  conditions  determine,  have 
no  manifest  co-ordination  of  parts.  In  the  Algce  the  Nostocs 
and  various  other  forms  similarly  show  us  an  unsymmetrical 
structure.  Of  Fungi  we  may  say  that  creeping  kinds  display 
no  further  dependence  of  one  part  on  another  than  is  implied 
by  their  cohesion.  And  even  in  such  better-organized  plants 
as  the  Marchantia,  the  general  arrangement  shows  no  refer- 
ence to  a  directive  centre.  Among  animals  many  of  the 
Sponges  in  their  adult  forms  may  be  cited  as  devoid  of  that 
co-ordination  implied  by  symmetry:  the  units  composing 
them,  though  they  have  some  subordination  to  local  centres, 
have  no  subordination  to  a  general  centre.  To  dis- 
tinguish that  kind  of  development  in  which  the  whole  product 
of  a  germ  coheres  in  one  mass,  from  that  kind  of  develop- 
ment in  which  it  does  not,  Professor  Huxley  has  introduced 
the  words  "  continuous "  and  "  discontinuous; "  and  these 
seem  the  best  fitted  for  the  purpose.  Multicentral  develop- 
ment, then,  is  divisible  into  continuous  and  discontinuous. 

•  From  central  development  we  pass  insensibly  to  that  higher 
kind  of  development  for  which  axial  seems  the  most  appro- 
priate name.  A  tendency  towards  this  is  vaguely  manifested 
almost  everywhere.  The  great  majority  even  of  Protopliyta 
and  Protozoa  have  different  longitudinal  and  transverse  di- 
mensions— have  an  obscure  if  not  a  distinct  axial  structure. 
The  originally  spheroidal  and  polyhedral  units  out  of  which 
higher  organisms  are  mainly  built,  usually  pass  into  shapes 


DEVELOPMENT.  16r> 

that  arc  subordinated  to  lines  rather  than  to  points.  And 
in  the  higher  organisms,  considered  as  wholes,  an  arrange- 
ment of  parts  in  relation  to  an  axis  is  distinct  and  nearly 
universal.  We  see  it  in  the  superior  orders  of  Thallophytes ; 
and  in  all  the  cormophytic  plants.  With  few  exceptions  the 
Cfflenterata  clearly  exhibit  it;  it  is  traceable,  though  less 
conspicuously,  throughout  the  Mollusca;  and  the  Annelida, 
Arthropoda,  and  Vertebrata  uniformly  show  it  with  perfect 
definiteness. 

This  kind  of  development,  like  the  first  kind,  is  of  two 
orders.  The  whole  germ-product  may  arrange  itself  round 
a  single  axis,  or  it  may  arrange  itself  round  many  axes :  the 
structure  may  be  uniaxial  or  multiaxial.  Each  division  of 
the  organic  kingdom  furnishes  examples  of  both  these 
orders.  In  such  Fungi  as  exhibit  axial  development 

at  all,  we  commonly  see  development  round  a  single  axis. 
Some  of  the  Algce,  as  the  common  tangle,  show  us  this 
arrangement.  And  of  the  higher  plants,  many  Monocotyle- 
dons and  small  Dicotyledons  are  uniaxial.  Of  animals,  the 
advanced  are  without  exception  in  this  category.  There  is 
no  known  vertebrate  in  which  the  whole  of  the  germ-product 
is  not  subordinated  to  a  single  axis.  In  the  Arthropoda, 
the  like  is  universal;  as  it  is  also  in  the  superior  orders  of 
Mollusca.  Multiaxial  development  occurs  in  most  of 

the  plants  we  are  familiar  with — every  branch  of  a  shrub  or 
tree  being  an  independent  axis.  But  while  in  the  vegetal 
kingdom  multiaxial  development  prevails  among  the  highest 
types,  in  the  animal  kingdom  it  prevails  only  among  the 
lowest  types.  It  is  extremely  general,  if  not  universal, 
among  the  Ccelenteraia;  it  is  characteristic  of  the  Polyzoa; 
the  compound  Ascidians  exhibit  it;  and  it  is  seen,  though 
under  another  form,  in  certain  of  the  inferior  Annelids. 

Development  that  is  axial,  like  development  that  is  central, 
may  be  either  continuous  or  discontinuous :  the  parts  having 
different  axes  may  continue  united,  or  they  may  separate. 

Instances  of  each  alternative  are  supplied  by  both  plants 
12 


166  THE  INDUCTIONS  OF  BIOLOGY. 

and  animals.  Continuous  multiaxial  development  is 

that  which  plants  usually  display,  and  need  not  be  illustrated 
further  than  by  reference  to  every  garden.  As  cases  of  it  in 
animals  may  be  named  all  the  compound  Hydrozoa  and  Ac- 
tinozoa;  and  such  ascidian  forms  as  the  Botryllidas.  Of 

multiaxial  development  that  is  discontinuous,  a  familiar 
instance  among  plants  exists  in  the  common  strawberry. 
This  sends  out  over  the  neighbouring  surface,  long  slender 
shoots,  bearing  at  their  extremities  buds  that  presently  strike 
roots  and  become  new  individuals;  and  these  by  and  by  lose 
their  connexions  with  the  original  axis.  Other  plants  there 
are  that  produce  certain  specialized  buds  called  bulbils,  which 
separating  themselves  and  falling  to  the  ground,  grow  into 
independent  plants.  Among  animals  the  fresh-water  polype 
very  clearly  shows  this  mode  of  development:  the  young 
polypes,  budding  out  from  its  surface,  severally  arrange 
their  parts  around  distinct  axes,  and  eventually  detaching 
themselves,  lead  separate  lives,  and  produce  other  polypes 
after  the  same  fashion.  By  some  of  the  lower  Annelida,  this 
multiplication  of  axes  from  an  original  axis,  is  carried  on 
after  a  different  manner:  the  string  of  segments  sponta- 
neously divides;  and  after  further  growth,  division  recurs  in 
one  or  both  of  the  halves.  Moreover  in  the  Syllls  ramosa, 
there  occurs  lateral  branching  also. 

Grouping  together  its  several  modes  as  above  delineated, 
we  see  that 

f    Unicentral 
Central  <  or         f    Continuous 

[  Multicentral  <  or 

DEVELOPMENT  is         or  I  Discontinuous 

{Uniaxial 
or  (    Continuous 

Multiaxial    4  or 

(^  Discontinuous 

Any  one  well   acquainted  with  the   facts,  may  readily 
raise  objections  to  this  arrangement.     He  may  name  forms 


DEVELOPMENT.  167 

which  do  not  ohviously  come  under  any  of  these  heads.  He 
may  point  to  plants  that  are  for  a  time  multicentral  but  after- 
wards develop  axially.  And  from  lower  -types  of  animals  he 
may  choose  many  in  which  the  continuous  and  discontinuous 
modes  are  both  displayed.  But,  as  already  hinted,  an  ar- 
rangement free  from  such  anomalies  must  be  impossible,  if 
the  various  kinds  of  organization  have  arisen  by  Evolution. 
The  one  above  sketched  out  is  to  be  regarded  as  a  rough 
grouping  of  the  facts,  which  helps  us  to  a  conception  of  them 
in  their  totality;  and,  so  regarded,  it  will  be  of  service  when 
we  come  to  treat  of  Individuality  and  Reproduction. 

§  51.  From  these  most  general  external  aspects  of  organic 
development,  let  us  now  turn  to  its  internal  and  more  special 
aspects.  When  treating  of  Evolution  as  a  universal  process 
of  things,  a  rude  outline  of  the  course  of  structural  changes  in 
organisms  was  given  (First  Principles,  §§  110,  119,  132). 
Here  it  will  be  proper  to  describe  these  changes  more  fully. 

The  bud  of  any  common  flowering  plant  in  its  earliest 
stage,  consists  of  a  small  hemispherical  or  sub-conical  pro- 
jection. While  it  increases  most  rapidly  at  the  apex,  this 
presently  develops  on  one  side  of  its  base,  a  smailer  projec- 
tion of  like  general  shape  with  itself.  Here  is  the  rudiment 
of  a  leaf,  which  presently  spreads  more  or  less  round  the  base 
of  the  central  hemisphere  or  main  axis.  At  the  same  time 
that  the  central  hemisphere  rises  higher,  this  lateral  promi- 
nence, also  increasing,  gives  rise  to  subordinate  prominences 
or  lobes.  These  are  the  rudiments  of  stipules,  where  the 
leaves  are  stipulated.  Meanwhile,  towards  the  other  side  of 
the  main  axis  and  somewhat  higher  up,  another  lateral  pro- 
minence arising  marks  the  origin  of  a  second  leaf.  By  the 
time  that  the  first  leaf  has  produced  another  pair  of  lobes, 
and  the  second  leaf  has  produced  its  primary  pair,  the  central 
hemisphere,  still  increasing  at  its  apex,  exhibits  the  rudiment 
of  a  third  leaf.  Similarly  throughout.  While  the  germ  of 
each  succeeding  leaf  thus  arises,  the  germs  of  the  previous 


168  THE  INDUCTIONS  OF  BIOLOGY. 

leaves,  in  the  order  of  their  priority,  are  changing  their  rude 
nodulated  shapes  into  flattened-out  expansions;  which  slowly 
put  on  those  sharp  outlines  they  show  when  unfolded.  Thus 
from  that  extremely  indefinite  figure,  a  rounded  lump,  giving 
off  from  time  to  time  lateral  lumps,  which  severally  becom- 
ing symmetrically  lobed  gradually  assume  specific  and  in- 
volved forms,  we  pass  little  by  little  to  that  comparatively 
complex  thing — a  leaf-bearing  shoot.  Internally,  a 

bud  undergoes  analogous  changes ;  as  witness  this  account : — 
"  The  general  mass  of  thin-walled  parenchymatous  cells 
which  occupies  the  apical  region,  and  forms  the  growing  point 
of  the  shoot,  is  covered  by  a  single  external  layer  of  similar 
cells,  which  increase  in  number  by  the  formation  of  new 
walls  in  one  direction  only,  perpendicular  to  the  surface  of 
the  shoot,  and  thus  give  rise  only  to  the  epidermis  or  single 
layer  of  cells  covering  the  whole  surface  of  the  shoot. 
Meanwhile  the  general  mass  below  grows  as  a  whole,  its 
constituent  cells  dividing  in  all  directions.  Of  the  new  cells 
so"  formed,  those  removed  by  these  processes  of  growth  and 
division  from  the  actual  apex,  begin,  at  a  greater  or  less  dis- 
tance from  it,  to  show  signs  of  the  differentiation  which  will 
ultimately  lead  to  the  formation  of  the  various  tissues  en- 
closed by  the  epidermis  of  the  shoot.  First  the  pith,  then 
the  vascular  bundles,  and  then  the  cortex  of  the  shoot,  begin 
to  take  on  their  special  characters."  Similarly  with  second- 
ary structures,  as  the  lateral  buds  whence  leaves  arise.  In 
the,  at  first,  unorganized  mass  of  cells  constituting  the  rudi- 
mentary leaf,  there  are  formed  vascular  bundles  which 
eventually  become  the  veins  of  the  leaf ;  and  pari  passu  with 
these  are  formed  the  other  tissues  of  the  leaf.  Nor 

do  we  fail  to  find  an  essentially  parallel  set  of  changes,  when 
we  trace  the  histories  of  the  individual  cells.  While  the 
tissues  they  compose  are  separating,  the  cells  are  growing 
step  by  step  more  unlike.  Some  become  flat,  some  poly- 
hedral, some  cylindrical,  some  prismatic,  some  spindle-shaped. 
These  develop  spiral  thickenings  in  their  interiors;  and 


DEVELOPMENT.  169 

those,  reticulate  thickenings.  Here  a  number  of  cells  unite 
together  to  form  a  tube :  and  there  they  become  almost  solid 
by  the  internal  deposition  of  woody  or  other  substance. 
Through  such  changes,  too  numerous  and  involved  to  be  here 
detailed,  the  originally  uniform  cells  go  on  diverging  and  re- 
diverging  until  there  are  produced  various  forms  that  seem 
to  have  very  little  in  common. 

The  arm  of  a  man  makes  its  first  appearance  in  as  simple 
a  way  as  does  the  shoot  of  a  plant.  According  to  Bischoff,  it 
buds-out  from  the  side  of  the  embryo  as  a  little  tongue-shaped 
projection,  presenting  no  differences  of  parts;  and  it  might 
serve  for  the  rudiment  of  some  one  of  the  various  other  organs 
that  also  arise  as  buds.  Continuing  to  lengthen,  it  presently 
becomes  somewhat  enlarged  at  its  end;  and  is  then  described 
as  a  pedicle  bearing  a  flattened,  round-edged  lump.  This 
lump  is  the  representative  of  the  future  hand,  and  the  pedicle 
of  the  future  arm.  By  and  by,  at  the  edges  of  this  flattened 
lump,  there  appear  four  clefts,  dividing  from  each  other  the 
buds  of  the  future  fingers ;  and  the  hand  as  a  whole  grows  a 
little  more  distinguishable  from  the  arm.  Up  to  this  time  the 
pedicle  has  remained  one  continuous  piece,  but  it  now  begins 
to  show  a  bend  at  its  centre,  which  indicates  the  division  into 
arm  and  forearm.  The  distinctions  thus  rudely  indicated 
gradually  increase :  the  fingers  elongate  and  become  jointed, 
and  the  proportions  of  all  the  parts,  originally  very  un- 
like those  of  the  complete  limb,  slowly  approximate  to 
them.  During  its  bud-like  stage,  the  rudimentary 

arm  consists  only  of  partially-differentiated  tissues.  By 
the  diverse  changes  these  gradually  undergo  they  are  trans- 
formed into  bones,  muscles,  blood-vessels,  and  nerves.  The 
extreme  softness  and  delicacy  of  these  primary  tissues, 
renders  it  difficult  to  trace  the  initial  stages  of  the  dif- 
ferentiations. In  consequence  of  the  colour  of  their  con- 
tents, the  blood-vessels  are  the  first  parts  to  become  distinct. 
Afterwards  the  cartilaginous  parts,  which  are  the  bases  of 
the  future  bones,  become  marked  out  by  the  denser  aggrega- 


170  THE  INDUCTIONS  OF   BIOLOGY. 

tion  of  their  constituent  cells,  and  by  the  production  between 
these  of  a  hyaline  substance  which  unites  them  into  a  trans- 
lucent mass.  When  first  perceptible,  the  muscles  are  gela- 
tinous, pale,  yellowish,  transparent,  and  indistinguishable 
from  their  tendons.  The  various  other  tissues  of  which 
the  arm  consists,  beginning  with  very  faintly-marked  differ- 
ences, become  day  by  day  more  definite  in  their  qualitative 
appearances.  In  like  manner  the  units  composing 

these  tissues  severally  assume  increasingly-specific  characters. 
The  fibres  of  muscle,  at  first  made  visible  in  the  midst  of 
their  gelatinous  matrix  only  by  immersion  in  alcohol,  grow 
more  numerous  and  distinct;  and  by  and  by  they  begin  to 
exhibit  transverse  stripes.  The  bone-cells  put  on  by  degrees 
their  curious  structure  of  branching  canals.  And  so  in  their 
respective  ways  with  the  units  of  skin  and  the  rest. 

Thus  in  each  of  the  organic  sub-kingdoms,  we  see  this 
change  from  an  incoherent,  indefinite  homogeneity  to  a 
coherent,  definite  heterogeneity,  illustrated  in  a  quadruple 
way.  The  originally-like  units  called  cells,  become  unlike  in 
various  ways,  and  in  ways  more  numerous  and  marked  as 
the  development  goes  on.  The  several  tissues  which  these 
several  classes  of  cells  form  by  aggregation,  grow  little  by 
little  distinct  from  each  other;  and  little  by  little  put  on 
those  structural  complexities  that  arise  from  differentiations 
among  their  component  units.  In  the  shoot,  as  in  the  limb, 
the  external  form,  originally  very  simple,  and  having  much 
in  common  with  simple  forms  in  general,  gradually  acquires 
an  increasing  complexity,  and  an  increasing  unlikeness  to 
other  forms.  Meanwhile,  the  remaining  parts  of  the  organism 
to  which  the  shoot  or  limb  belongs,  having  been  severally 
assuming  structures  divergent  from  one  another  and  from 
that  of  this  particular  shoot  or  limb,  there  has  arisen  a 
greater  heterogeneity  in  the  organism  as  a  whole. 

§  52.  One  of  the  most  remarkable  inductions  of  embry- 
ology comes  next  in  order.  And  here  we  find  illustrated 


DEVELOPMENT.  171 

the  general  truth  that  in  mental  evolution  as  in  bodily  evo- 
lution the  progress  is  from  the  indefinite  and  inexact  to  the 
definite  and  exact.  For  the  first  statement  of  this  induction 
was  but  an  adumbration  of  the  correct  statement. 

As  a  result  of  his  examinations  von  Baer  alleged  that  in 
its  earliest  stage  every  organism  has  the  greatest  number  of 
characters  in  common  with  all  other  organisms  in  their 
earliest  stages;  that  at  a  stage  somewhat  later  its  structure 
is  like  the  structures  displayed  at  corresponding  phases  by  a 
less  extensive  assemblage  of  organisms;  that  at  each  sub- 
sequent stage  traits  are  acquired  which  successively  distin- 
guish the  developing  embryo  from  groups  of  embryos  that  it 
previously  resembled — thus  step  by  step  diminishing  the 
group  of  embryos  which  it  still  resembles ;  and  that  thus  the 
class  of  similar  forms  is  finally  narrowed  to  the  species  of 
which  it  is  a  member.  This  abstract  proposition  will  per- 
haps not  be  fully  comprehended  by  the  general  reader.  It 
will  be  best  to  re-state  it  in  a  concrete  shape.  Sup- 

posing the  germs  of  all  kinds  of  organisms  to  be  simul- 
taneously developing,  we  may  say  that  all  members  of  the 
vast  multitude  take  their  first  steps  in  the  same  direction; 
that  at  the  second  step  one-half  of  this  vast  multitude  di- 
verges from  the  other  half,  and  thereafter  follows  a  different 
course  of  development;  that  the  immense  assemblage  con- 
tained in  either  of  these  divisions  very  soon  again  shows  a 
tendency  to  take  two  or  more  routes  of  development;  that 
each  of  the  two  or  more  minor  assemblages  thus  resulting, 
shows  for  a  time  but  small  divergences  among  its  members, 
but  presently  again  divides  into  groups  which  separate  ever 
more  widely  as  they  progress ;  and  so  on  until  each  organism, 
when  nearly  complete,  is  accompanied  in  its  further  modifi- 
cations only  by  organisms  of  the  same  species;  and  last  of 
all,  assumes  the  peculiarities  which  distinguish  it  as  an  indi- 
vidual— diverges  to  a  slight  extent  to  the  organisms  it  is 
most  like. 

But,  as  above  said,  this  statement  is  only  an  adumbration. 


172  THE  INDUCTIONS  OF  BIOLOGY. 

The  order  of  Nature  is  habitually  more  complex  than  our 
generalizations  represent  it  as  being — refuses  to  be  fully 
expressed  in  simple  formulae;  and  we  are  obliged  to  limit 
them  by  various  qualifications.  It  is  thus  here.  Since  von 
Baer's  day  the  careful  observations  of  numerous  observers 
have  shown  his  allegation  to  be  but  approximately  true. 
Hereafter,  when  discussing  the  embryological  evidence  of 
Evolution,  the  causes  of  deviations  will  be  discussed.  For 
the  present  it  suffices  to  recognize  as  unquestionable  the  fact 
that  whereas  the  germs  of  organisms  are  extremely  similar, 
they  gradually  diverge  widely,  in  modes  now  regular  and 
now  irregular,  until  in  place  of  a  multitude  of  forms  practi- 
cally alike  we  finally  have  a  multitude  of  forms  most  of 
which  are  extremely  unlike.  Thus,  in  conformity  with  the 
law  of  evolution,  not  only  do  the  parts  of  each  organism 
advance  from  indefinite  homogeneity  to  definite  hetero- 
geneity, but  the  assemblage  of  all  organisms  does  the  same: 
a  truth  already  indicated  in  First  Principles. 

§  53.  This  comparison  between  the  course  of  development 
in  any  creature,  and  the  course  of  development  in  all  other 
creatures — this  arrival  at  the  conclusion  that  the  course  of 
development  in  each,  at  first  the  same  as  in  all  others,  be- 
comes stage  by  stage  differentiated  from  the  courses  in  all 
others,  brings  us  within  view  of  an  allied  conclusion.  If  we 
contemplate  the  successive  stages  passed  through  by  any 
higher  organism,  and  observe  the  relation  between  it  and  its 
environment  at  each  of  these  stages;  we  shall  sec  that  this 
relation  is  modified  in  a  way  analogous  to  that  in  which  the 
relation  between  the  organism  and  its  environment  is  modi- 
fied, as  we  advance  from  the  lowest  to  the  highest  grades. 
Along  with  the  progressing  differentiation  of  each  organism 
from  others,  we  find  a  progressing  differentiation  of  it  from 
its  environment;  like  that  progressing  differentiation  from 
the  environment  which  we  meet  with  in  the  ascending  forms 
of  life.  Let  us  first  glance  at  the  way  in  which  the  ascend- 


DEVELOPMENT.  173 

ing  forms  of  life  exhibit  this  progressing  differentiation  from 
the  environment. 

In  the  first  place,  it  is  illustrated  in  structure.  Advance 
from  the  homogeneous  to  the  heterogeneous,  itself  involves 
an  increasing  distinction  from  the  inorganic  world.  Passing 
over  the  Protozoa,  of  which  the  simplest  probably  dis- 
appeared during  the  earliest  stages  of  organic  evolution,  and 
limiting  our  comparison  to  the  Metazoa,  we  see  that  low 
types  of  these,  as  the  Ccelentcrata,  are  relatively  simple  in 
their  organization;  and  the  ascent  to  organisms  of  greater 
and  greater  complexity  of  structure,  is  an  ascent  to  organisms 
which  are  in  that  respect  more  strongly  contrasted  with  the 
structureless  environment.  In  form,  again,  we  see 

the  same  truth.  An  ordinary  characteristic  of  inorganic 
matter  is  its  indefiniteness  of  form;  and  this  is  also  a  cha- 
racteristic of  the  lower  organisms,  as  compared  with  the 
higher.  Speaking  generally,  plants  are  less  definite  than 
animals,  both  in  shape  and  size — admit  of  greater  modifica- 
tions from  variations  of  position  and  nutrition.  Among  ani- 
mals, the  simplest  Ehizopods  may  almost  be  called  amor- 
phous :  the  form  is  never  specific,  and  is  constantly  changing. 
Of  the  organisms  resulting  from  the  aggregation  of  such 
creatures,  we  see  that  while  some,  as  the  Foraminifera,  as- 
sume a  certain  definiteness  of  form,  in  their  shells  at  least, 
others,  as  the  Sponges,  are  very  irregular.  The  Zoophytes 
and  the  Polyzoa  are  compound  organisms,  most  of  which 
have  a  mode  of  growth  not  more  determinate  than  that  of 
plants.  But  among  the  higher  animals,  we  find  not  only  that 
the  mature  shape  of  each  species  is  very  definite,  but  that  the 
individuals  of  each  species  differ  little  in  size.  A 

parallel  increase  of  contrast  is  seen  in  chemical  composition. 
With  but  few  exceptions,  and  those  only  partial  ones,  the 
lowest  animal  and  vegetal  forms  are  inhabitants  of  the 
water;  and  water  is  almost  their  sole  constituent.  Desic- 
cated Protophyta  and  Protozoa  shrink  into  mere  dust;  and 
among  the  Acalephes  we  find  but  a  few  grains  of  solid  matter 


174  THE  INDUCTIONS  OF  BIOLOGY. 

to  a  pound  of  water.  The  higher  aquatic  plants,  in  common 
with  the  higher  aquatic  animals,  possessing  as  they  do  in- 
creased tenacity  of  substance,  also  contain  a  greater  propor- 
tion of  the  organic  elements ;  further  they  show  us  a  greater 
variety  of  composition  in  their  different  parts;  and  thus  in 
both  ways  are  chemically  more  unlike  their  medium.  And 
when  we  pass  to  the  superior  classes  of  organisms — land- 
plants  and  land-animals — we  see  that,  chemically  considered, 
they  have  little  in  common  either  with  the  earth  on  which 
they  stand  or  the  air  which  surrounds  them.  In 

specific  gravity  too,  we  may  note  a  like  truth.  The  simplest 
forms,  in  common  with  the  spores  and  gemmules  of  higher 
ones,  are  as  nearly  as  may  be  of  the  same  specific  gravity  as 
the  water  in  which  they  float;  and  though  it  cannot  be  said 
that  among  aquatic  creatures,  superior  specific  gravity  is  a 
standard  of  general  superiority,  yet  we  may  fairly  say  that 
the  higher  orders  of  them,  ivhen  divested  of  the  appliances 
by  which  their  specific  gravity  is  regulated,  differ  more  from 
water  in  their  relative  weights  than  do  the  lowest.  In  ter- 
restrial organisms,  the  contrast  becomes  marked.  Trees  and 
plants,  in  common  with  insects,  reptiles,  mammals,  birds,  are 
all  of  a  specific  gravity  considerably  less  than  that  of  the 
earth  and  immensely  greater  than  that  of  the  air.  Yet 

further,  we  see  the  law  fulfilled  in  respect  of  temperature. 
Plants  generate  but  extremely  small  quantities  of  heat,  which 
are  to  be  detected  only  by  delicate  experiments;  and  prac- 
tically they  may  be  considered  as  having  the  same  tempera- 
ture as  their  environment.  The  temperature  of  aquatic 
animals  is  very  little  above  that  of  the  surrounding  water: 
that  of  the  invertebrata  being  mostly  less  than  a  degree  above 
it,  and  that  of  fishes  not  exceeding  it  by  more  than  two  or 
three  degrees;  save  in  the  case  of  some  large  red-blooded 
fishes,  as  the  tunny,  which  exceed  it  in  temperature  by  nearly 
ten  degrees.  Among  insects  the  range  is  from  two  to  ten 
degrees  above  that  of  the  air:  the  excess  varying  according 
to  their  activity.  The  heat  of  reptiles  is  from  four  to  fifteen 


DEVELOPMENT.  175 

degrees  more  than  the  heat  of  their  medium.  While  mam- 
mals and  birds  maintain  a  heat  which  continues  almost  un- 
affected by  external  variations,  and  is  often  greater  than  that 
of  the  air  by  seventy,  eighty,  ninety,  and  even  a  hundred 
degrees.  Once  more,  in  greater  self-mobility  a  pro- 

gressive differentiation  is  traceable.  The  chief  characteristic 
by  which  we  distinguish  dead  matter  is  its  inertness:  some 
form  of  independent  motion  is  our  most  familiar  proof  of 
life.  Passing  over  the  indefinite  border-land  between  the 
animal  and  vegetal  kingdoms,  we  may  roughly  class  plants 
as  organisms  which,  while  they  exhibit  that  kind  of  motion 
implied  in  growth,  are  not  only  devoid  of  locomotive  power, 
but  with  some  unimportant  exceptions  are  devoid  of  the 
power  of  moving  their  parts  in  relation  to  each  other;  and 
thus  are  less  differentiated  from  the  inorganic  world  than 
animals.  Though  in  those  microscopic  Protophyta  and  Pro- 
tozoa inhabiting  the  water  we  see  locomotion  produced  by 
ciliary  action;  yet  this  locomotion,  while  rapid  relatively  to 
the  sizes  of  their  bodies,  is  absolutely  slow.  Of  the  Coelen- 
terata  a  great  part  are  either  permanently  rooted  or  habitu- 
ally stationary;  and  so  have  scarcely  any  self-mobility  but 
that  implied  in  the  relative  movements  of  parts;  while  the 
rest,  of  which  the  common  jelly-fish  serves  as  a  sample,  have 
mostly  but  little  ability  to  move  themselves  through  the 
water.  Among  the  higher  aquatic  7nver£e&ra£a,^-cuttlefishes 
and  lobsters,  for  instance, — there  is  a  very  considerable  power 
of  locomotion;  and  the  aquatic  Vertebrata  are,  considered  as 
a  class,  much  more  active  in  their  movements  than  the  other 
inhabitants  of  the  water.  But  it  is  only  when  we  come  to 
air-breathing  creatures  that  we  find  the  vital  characteristics  of 
self -mobility  manifested  in  the  highest  degree.  Flying  insects, 
mammals,  birds,  travel  with  velocities  far  exceeding  those 
attained  by  any  of  the  lower  classes  of  animals.  Thus, 

on  contemplating  the  various  grades  of  organisms  in  their 
ascending  order,  we  find  them  more  and  more  distinguished 
from  their  inanimate  media,  in  structure,  in  form,  in  chemical 


170  THE  INDUCTIONS  OF  BIOLOGY. 

composition,  in  specific  gravity,  in  temperature,  in  self -mobil- 
ity. It  is  true  that  this  generalization  does  not  hold  with  com- 
plete regularity.  Organisms  which  are  in  some  respects  the 
most  strongly  contrasted  with  the  environing  inorganic  world, 
are  in  other  respects  less  contrasted  than  inferior  organisms. 
As  a  class,  mammals  are  higher  than  hirds ;  and  yet  they  are 
of  lower  temperature  and  have  smaller  powers  of  locomotion. 
The  stationary  oyster  is  of  higher  organization  than  the  free- 
swimming  medusa;  and  the  cold-blooded  and  less  hetero- 
geneous fish  is  quicker  in  its  movements  than  the  warm- 
blooded and  more  heterogeneous  sloth.  But  the  admission 
that  tb,e  several  aspects  under  which  this  increasing  contrast 
shows  itselfybear  variable  ratios  to  each  other,  does  not  con- 
flict with  the  general  truth  that  as  we  ascend  in  the  hierarchy 
of  organisms,  we  meet  with  not  only  an  increasing  differen- 
tiation of  parts  but  also  an  increasing  differentiation  from 
the  surrounding  medium  in  sundry  other  physical  attributes. 
It  would  seem  that  this  trait  has  some  necessary  connexion 
with  superior  vital  manifestations.  One  of  those  lowly 
gelatinous  forms,  so  transparent  and  colourless  as  to  be  with 
difficulty  distinguished  from  the  water  it  floats  in,  is  not 
more  like  its  medium  in  chemical,  mechanical,  optical, 
thermal,  and  other  properties,  than  it  is  in  the  passivity  with 
which  it  submits  to  all  the  influences  and  actions  brought  to 
bear  upon  it ;  while  the  mammal  docs  not  more  widely  differ 
from  inanimate  things  in  these  properties,  than  it  does  in  the 
activity  with  which  it  meets  surrounding  changes  by  com- 
pensating changes  in  itself.  And  between  these  extremes, 
these  two  kinds  of  contrast  vary  together.  So  that  in  pro- 
portion as  an  organism  is  physically  like  its  environment  it 
remains  a  passive  partaker  of  the  changes  going  on  in  its 
environment;  while  in  proportion  as  it  is  endowed  with 
powers  of  counteracting  such  changes,  it  exhibits  greater  un- 
likeness  to  its  environment.* 

*  This  paragraph  01  initially  formed  part  of  a  review-article  on  "  Trans- 
cendental Physiology,"  published  in  1857. 


DEVELOPMENT.  17? 

I  f  now,  from  this  same  point  of  view,  we  consider  the  rela- 
tion borne  to  its  environment  by  any  superior  organism  in 
its  successive  stages,  we  find  an  analogous  series  of  con- 
trasts. Of  course  in  respect  of  degrees  of  structure  the 
parallelism  is  complete.  The  difference,  at  first  small,  be- 
tween the  little-structured  germ  and  the  little-structured  in- 
organic world,  necessarily  becomes  greater,  step  by  step,  as 
the  differentiations  of  the  germ  become  more  numerous  and 
definite.  How  of  form  the  like  holds  is  equally  mani- 
fest- The  sphere,  which  is  the  point  of  departure  common  to 
all  organisms,  is  the  most  generalized  of  figures ;  and  one  that 
is,  under  various  circumstances,  assumed  by  inorganic  matter. 
But  as  it  develops  it  loses  all  likeness  to  inorganic  objects  in 
the  environment ;  and  eventually  becomes  distinct  even  from 
nearly  all  organic  objects  in  its  environment.  In 
specific  gravity  the  alteration,  though  not  very  marked,  is  still 
in  the  same  direction.  Development  being  habitually  accom- 
panied by  a  relative  decrease  in  the  quantity  of  water  and  an 
increase  in  the  quantity  of  constituents  that  are  heavier 
than  water,  there  results  a  small  augmentation  of  relative 
weight.  In  power  of  maintaining  a  temperature  above 
that  of  surrounding  things,  the  differentiation  from  the  en- 
vironment that  accompanies  development  is  marked.  All 
ova  are  absolutely  dependent  for  their  heat  on  external 
sources.  The  mammalian  young  one  is,  during  its  uterine 
life,  dependent  on  the  maternal  heat;  and  at  birth  has 
but  a  partial  power  of  making  good  the  loss  by  radiation. 
But  as  it  advances  in  development  it  gains  an  ability  to 
maintain  a  constant  temperature  above  that  of  surrounding 
things:  so  becoming  markedly  unlike  them.  Lastly, 
in  self-mobility  this  increasing  contrast  is  no  less  decided. 
Save  in  a  few  aberrant  tribes,  chiefly  parasitic,  we  find  the 
general  fact  to  be  that  the  locomotive  power,  totally  absent 
or  very  small  at  the  outset,  increases  with  the  advance 
towards  maturity.  The  more  highly  developed  the  organism 
I  '  •  ' 


178  THE  INDUCTIONS  OP  BIOLOGY. 

becomes,  the  stronger  grows  the  contrast  between  its  activity 
and  the  inertness  of  the  objects  amid  which  it  moves. 

Thus  we  may  say  that  the  development  of  an  individual 
organism,  ifl  at  the  same  time  a  differentiation  of  its  part* 
from  each  other,  and  a  differentiation  of  the  consolidated 
whole  from  the  environment ;  and  that  in  the  last  as  in  the 
first  respect,  there  is  a  general  analogy  between  the  progres- 
sion of  an  individual  organism  and  the  progression  from  the 
lowest  orders  of  organisms  to  the  highest  orders.  It 

may  be  remarked  that  some  kinship  seems  to  exist  between 
these  generalizations  and  the  doctrine  of  Schelling,  that  Life 
is  the  tendency  to  individnation.  For  evidently,  in  becoming 
more  distinct  from  one  another  and  from  their  environment, 
organisms  acquire  more  marked  individualities.  As  far  as  I 
can  gather  from  outlines  of  his  philosophy,  however,  Schelling 
entertained  this  conception  in  a  general  and  transcendental 
sense,  rather  than  in  a  special  and  scientific  one. 

§  54.  Deductive  interpretations  of  these  general  facts  of 
development,  in  so  far  as  they  are  possible,  must  be  post- 
poned until  we  arrive  at  the  fourth  and  fifth  divisions  of  this 
work.  There  are,  however,  one  or  two  general  aspects  of 
these  inductions  which  may  be  here  conveniently  dealt  with 
deductively. 

Grant  that  each  organism  is  at  the  outset  relatively  homo- 
geneous and  that  when  complete  it  is  relatively  heterogeneous, 
and  it  necessarily  follows  that  development  is  a  change  from 
the  homogeneous  to  the  heterogeneous — a  change  during 
which  there  must  be  gone  through  all  the  gradations  of 
heterogeneity  that  lie  between  these  extremes.  If,  again, 
there  is  at  first  indefiniteness  and  at  last  definiteness,  the 
transition  cannot  but  be  from  the  one  to  the  other  of  these 
through  all  intermediate  degrees  of  definiteness.  Further,  if 
the  parts,  originally  incoherent  or  nncombined,  eventually  be- 
come relatively  coherent  or  combined,  there  must  be  a  con- 
tinuous increase  of  coherence  or  combination.  Hence  the 


DEVELOPMENT.  179 

general  truth  that  development  is  a  change  from  incoherent, 
indefinite  homogeneity,  to  coherent,  definite  heterogeneity, 
becomes  a  self-evident  one  when  observation  has  shown  us 
the  state  in  which  organisms  begin  and  the  state  in  which 
they  end. 

Just  in  the  same  way  that  the  growth  of  an  entire  organ- 
ism is  carried  on  by  abstracting  from  the  environment 
substances  like  those  composing  the  organism;  so  the  pro- 
duction of  each  organ  within  the  organism  is  carried  on  by 
abstracting  from  the  substances  contained  in  the  organism, 
those  required  by  this  particular  organ.  Each  organ  at  the 
expense  of  the  organism  as  a  whole,  integrates  with  itself 
certain  kinds  and  proportions  of  the  matters  circulating 
around  it;  in  the  same  way  that  the  organism  as  a  whole, 
integrates  with  itself  certain  kinds  and  proportions  of 
matters  at  the  expense  of  the  environment  as  a  whole.  So 
that  the  organs  are  qualitatively  differentiated  from  each 
other,  in  a  way  analogous  to  that  by  which  the  entire  organ- 
ism is  qualitatively  differentiated  from  things  around 
it.  Evidently  this  selective  assimilation  illustrates 

the  general  truth,  set  forth  and  illustrated  in  First  Principles, 
that  like  units  tend  to  segregate.  It  illustrates,  moreover, 
the  further  aspect  of  this  general  truth,  that  the  pre-exist- 
ence  of  a  mass  of  certain  units  produces  a  tendency  for 
diffused  units  of  the  same  kind  to  aggregate  with  this  mass 
rather  than  elsewhere.  It  has  been  shown  of  particular  salts, 
A  and  B,  co-existing  in  a  solution  not  sufficiently  concen- 
trated to  crystallize,  that  if  a  crystal  of  the  salt  A  be  put 
into  the  solution,  it  will  increase  by  uniting  with  itself  the 
dissolved  atoms  of  the  salt  A;  and  that  similarly,  though 
there  otherwise  takes  place  no  deposition  of  the  salt  B,  yet  if 
a  crystal  of  the  salt  B  is  placed  in  the  solution,  it  will  exer- 
cise a  coercive  force  on  the  diffused  atoms  of  this  salt,  and 
grow  at  their  expense.  ProVably  much  organic  assimilation 
occurs  in  the  same  way.  Particular  parts  of  the  organism 
are  composed  of  special  units)  or  have  the  function  of  secret- 


180  THE  INDUCTIONS  OF  BIOLOGY. 

ing  special  units,  which  are  ever  present  in  them  in  large 
quantities.  The  fluids  circulating  through  the  body  contain 
special  units  of  this  same  order.  And  these  diffused  units 
are  continually  being  deposited  along  with  the  groups  of  like 
units  that  already  exist.  How  purely  physical  are  the 
causes  of  this  selective  assimilation,  is,  indeed,  shown  by  the 
fact  that  abnormal  constituents  of  the  blood  are  segregated 
in  the  same  way.  The  chalky  deposits  of  gout  beginning  at 
certain  points,  collect  more  and  more  around  those  points. 
And  similarly  in  numerous  pustular  diseases.  Where 

the  component  units  of  an  organ,  or  some  of  them,  do  not 
exist  as  such  in  the  circulating  fluids,  but  are  formed  out  of 
elements  or  compounds  that  exist  separately  in  the  circulat- 
ing fluids,  the  process  of  differential  assimilation  must  be  of 
a  more  complex  kind.  Still,  however,  it  seems  not  impossi- 
ble that  it  is  carried  on  in  an  analogous  way.  If  there  be  an 
aggregate  of  compound  atoms,  each  of  which  contains  the 
constituents  A,  B,  C;  and  if  round  this  aggregate  the  con- 
stituents A  and  B  and  C  are  diffused  in  uncombined  states; 
it  may  be  suspected  that  the  coercive  force  of  these  aggre- 
gated compound  atoms  A,  B,  C,  may  not  only  bring  into 
union  with  themselves  adjacent  compound  atoms  A,  B,  C,  but 
may  cause  the  adjacent  constituents  A  and  B  and  C  to 
unite  into  such  compound  atoms,  and  then  aggregate  with 
the  mass. 


CHAPTER  IIA. 

STRUCTURE.* 

§  54a.  As,  in  the  course  of  evolution,  we  rise  from  the 
smallest  to  the  largest  aggregates  by  a  process  of  integration, 
so  do  we  rise  by  a  process  of  differentiation  from  the  simplest 
to  the  most  complex  aggregates.  The  initial  types  of  life  are 
at  once  extremely  small  and  almost  structureless.  Passing 
over  those  which  swarm  in  the  air,  the  water,  and  the  soil, 
and  are  now  some  of  them  found  to  be  causes  of  diseases,  we 
may  set  out  with  those  ordinarily  called  Protozoa  and  Pro- 
topliyta:  the  lowest  of  which,  however,  are  either  at  once 
plants  and  animals,  or  are  now  one  and  now  the  other. 

That  the  first  living  things  were  minute  portions  of  simple 
protoplasm  is  implied  by  the  general  theory  of  Evolution; 
but  we  have  no  evidence  that  such  portions  exist  now.  Even 
admitting  that  there  are  protoplasts  (using  this  word  to  in- 
clude plant  and  animal  types)  which  are  without  nuclei,  still 
they  are  not  homogeneous — they  are  granular.  Whether  a 
nucleus  is  always  present  is  a  question  still  undecided;  but 
in  any  case  the  types  from  which  it  is  absent  are  extremely 
exceptional.  Thus  the  most  general  structural  traits  of  pro- 
toplasts are — the  possession  of  an  internal  part,  morpho- 

*  When,  in  1863,  the  preceding  chapter  was  written,  it  had  not  occurred 
to  me  that  there  needed  an  accompanying  chapter  treating  of  Structure. 
The  gap  left  by  that  oversight  I  now  fill  up.  In  doing  this  there  have  been 
included  certain  statements  which  are  tacitly  presupposed  in  the  last  chap- 
ter, and  there  may  also  be  some  which  overlap  statemen!  s  in  the  next  chapter. 
I  have  not  thought  it  needful  so  to  alter  adjacent  chapters  as  to  remove  these 
slight  defects :  the  duplicated  ideas  will  bear  re-emphasizing. 

13  181 


182  THE  INDUCTIONS  OF  BIOLOGY. 

logically  central  though  often  not  centrally  situated,  a  general 
mass  of  protoplasm  surrounding  it,  and  an  inclosing  differ- 
entiated portion  in  contact  with  the  environment.  These  essen- 
tial elements  are  severally  subject  to  various  complications. 

In  some  simple  types  the  limiting  layer  or  cortical  sub- 
stance can  scarcely  be  said  to  exist  as  a  separate  element. 
The  exoplasm,  distinguished  from  the  endoplasm  by  absence 
or  paucity  of  granules,  is  continually  changing  places  with  it 
by  the  sending  out  of  pseudopodia  which  are  presently  drawn 
back  into  the  general  mass:  the  inner  and  outer,  being  un- 
settled in  position,  are  not  permanently  differentiated.  Then 
we  have  types,  exemplified  by  Lithamceba,  constituted  of 
protoplasm  covered  by  a  distinct  pellicle,  which  in  sundry 
groups  becomes  an  outer  shell  of  various  structure:  now 
jelly-like,  now  of  cellulose,  now  siliceous  or  calcareous. 
While  here  this  envelope  has  a  single  opening,  there  it  is 
perforated  all  over — a  fenestrated  shell.  In  some  cases  an 
external  layer  is  formed  of  agglutinated  sand-particles;  in 
others  of  imbricated  plates,  as  in  Coccospheres ;  and  in  many 
others  radiating  spicules  stand  out  on  all  sides.  Through- 
out sundry  classes  the  exoplasm  develops  cilia,  by  the  wavings 
of  which  the  creatures  are  propelled  through  the  water — 
cilia  which  may  be  either  general  or  local.  And  then  this 
cortical  layer,  instead  of  being  spherical  or  spheroidal,  may 
become  piano-spiral,  cyclical,  crosier-shaped,  and  often  many- 
chambered  ;  whence  there  is  a  transition  to  colonies. 

Meanwhile  the  inclosed  protoplasm,  at  first  little  more 
than  a  network  or  foamwork  containing  granules  and  made 
irregular  by  objects  drawn  in  as  nutriment,  becomes  vari- 
ously complicated.  In  some  low  types  its  continuity  is 
broken  by  motionless,  vacant  spaces,  but  in  higher  types 
there  are  contractile  vacuoles  slowly  pulsing,  and,  as  we  may 
suppose,  moving  the  contained  liquid  hither  and  thither; 
while  there  are  types  having  many  passive  vacuoles  along 
with  a  few  active  ones.  In  some  varieties  the  protruded 
parts,  or  pseudopodia,  into  which  the  protoplasm  continually 


STRUCTURE.  183 

shapes  itself,  are  comparatively  short  and  club-shaped;  in 
others  they  are  long  and  fine  filaments  which  anastomose, 
so  forming  a  network  running  here  and  there  into  little 
pools  of  protoplasm.  Then  there  are  kinds  in  which  the 
protoplasm  streams  up  and  down  the  protruding  spicules: 
sometimes  inside  of  them,  sometimes  outside.  Always,  too, 
there  is  included  in  the  protoplasm  a  small  body  known  as 
a  centrosome. 

Lastly,  we  have  the  innermost  element,  considered  the 
essential  element — the  nucleus.  According  to  Prof.  Lan- 
kester,  it  is  absent  from  ArcTierina,  and  there  are  types  in 
which  it  is  made  visible  only  by  the  aid  of  special  reagents. 
Ordinarily  it  is  marked  off  from  the  surrounding  protoplasm 
by  a  delicate  membrane,  just  as  the  protoplasm  itself  is 
marked  off  by  the  exoplasm  from  the  environment.  Most 
commonly  there  is  a  single  nucleus,  but  occasionally  there 
are  many,  and  sometimes  there  is  a  chief  one  with  minor 
ones.  Moreover,  within  the  nucleus  itself  there  have  of 
late  years  been  discovered  remarkable  structural  elements 
which  undergo  complicated  changes. 

These  brief  statements  indicate  only  the  most  general 
traits  of  an  immense  variety  of  structures — so  immense  a 
variety  that  Prof.  Lankester,  in  distinguishing  the  classes, 
sub-classes,  orders,  and  genera  in  the  briefest  way,  occupies 
37  quarto  pages  of  small  type.  And  to  give  a  corresponding 
account  of  Protopliyta  would  require  probably  something 
like  equal  space.  Thus  these  living  things,  so  minute  that 
unaided  vision  fails  to  disclose  them,  constitute  a  world  ex- 
hibiting varieties  of  structure  which  it  requires  the  devotion 
of  a  life  to  become  fully  acquainted  with. 

§  54&.  If  higher  forms  of  life  have  arisen  from  lower  forms 
by  evolution,  the  implication  is  that  there  must  once  have 
existed,  if  there  do'  not  still  exist,  transitional  forms ;  and 
there  follows  the  comment  that  there  do  still  exist  transi- 
tional forms.  Both  in  the  pi  ant- wo  rid  and  in  the  animal- 


184  THE  INDUCTIONS  OF  BIOLOGY. 

world  there  are  types  in  which  we  see  little  more  than 
simple  assemblages  of  Protophyta  or  of  Protozoa — types  in 
which  the  units,  though  coherent,  are  not  differentiated  but 
constitute  a  uniform  mass.  In  treating  of  structure  we  arc 
not  here  concerned  with  these  unstructured  types,  but  may 
pass  on  to  those  aggregates  of  protoplasts  which  show  us 
differentiated  parts — Metaphyta  and  Metazoa:  economizing 
space  by  limiting  our  attention  chiefly  to  the  last. 

When,  half  a  century  ago,  some  currency  was  given  to  the 
statement  that  all  kinds  of  organisms,  plant  and  animal, 
which  our  unaided  eyes  disclose,  are  severally  composed  of 
myriads  of  living  units,  some  of  them  partially,  if  not  com- 
pletely, independent,  and  that  thus  a  man  is  a  vast  nation  of 
minute  individuals  of  which  some  are  relatively  passive  and 
others  relatively  active,  the  statement  met,  here  with  in- 
credulity and  there  with  a  shudder.  But  what  was  then 
thought  a  preposterous  assertion  has  now  come  to  be  an 
accepted  truth. 

Along  with  gradual  establishment  of  this  truth  has  gone 
gradual  modification  in  the  form  under  which  it  was  origi- 
nally asserted.  If  some  inhabitant  of  another  sphere  were 
to  describe  one  of  our  towns  as  composed  exclusively  of 
houses,  saying  nothing  of  the  contained  beings  who  had  built 
them  and  lived  in  them,  we  should  say  that  he  had  made  a  pro- 
found error  in  recognizing  only  the  inanimate  elements  of 
the  town  and  disregarding  the  animate  elements.  Early 
histologists  made  an  analogous  error.  Plants  and  animals 
were  found  to  consist  of  minute  members,  each  of  which  ap- 
peared to  be  simply  a  wall  inclosing  a  cavity — a  cell.  But 
further  investigation  proved  that  the  content  of  the  cell, 
presently  distinguished  as  protoplasm,  is  its  essential  living 
part,  and  that  the  cell-wall,  when  present,  is  produced  by  it. 
Thus  the  unit  of  composition  is  a  protoplast,  usually  enclosed, 
with  its  contained  nucleus  and  centrosome. 

§  54c.  As  above  implied,  the  individualities  of  the  units 


STRUCTURE.  185 

are  not  wholly  lost  in  the  individuality  of  the  aggregate,  but 
continue,  some  of  them,  to  be  displayed  in  various  degrees : 
the  great  majority  of  them  losing  their  individualities  more 
and  more  as  the  type  of  the  aggregate  becomes  higher. 

In  a  slightly  organized  Metazoon  like  the  sponge,  the  sub- 
ordination is  but  small.  Only  those  members  of  the  aggre- 
gate which,  flattened  and  united  together,  form  the  outer 
layer  and  those  which  become  metamorphosed  into  spicules, 
have  entirely  lost  their  original  activities.  Of  the  rest  nearly 
all,  lining  the  channels  which  permeate  the  mass,  and  driving 
onwards  the  contained  sea-water  by  the  motions  of  their 
whip-like  appendages,  substantially  retain  their  separate 
lives;  and  beyond  these  there  exist  in  the  gelatinous  sub- 
stance lying  between  the  inner  and  outer  layers,  which  is 
regarded  as  homologous  with  a  mesoderm,  amoeba-form  proto- 
plasts which  move  about  from  place  to  place. 

Kelations  between  the  aggregate  and  the  units  which  are 
in  this  case  permanent,  are  in  other  cases  temporary:  cha- 
racterizing early  stages  of  embryonic  development.  For 
example,  drawings  of  Echinoderm  larva?  at  an  early  stage, 
show  us  the  potential  independence  of  all  the  cells  forming 
the  blastosphere ;  for  in  the  course  of  further  development 
some  of  these  resume  the  primitive  amoeboid  state,  migrate 
through  the  internal  space,  and  presently  unite  to  form 
certain  parts  of  the  growing  structures.  But  with  the  pro- 
gress of  organization  independence  of  this  kind  diminishes. 

Converse  facts  are  presented  after  development  has  been 
completed;  for  with  the  commencement  of  reproduction  we 
everywhere  see  more  or  less  resumption  of  individual  life 
among  the  units,  or  some  of  them.  It  is  a  trait  of  transi- 
tional types  between  Protozoa  and  Metazoa  to  lead  an  aggre- 
gate life  as  a  plasmodium,  and  then  for  this  to  break  up 
into  its  members,  which  for  a  time  lead  individual  lives  as 
generative  agents ;  and  sundry  low  kinds  of  plants  possessing 
small  amounts  of  structure,  have  generative  elements — 
ZQospores  and  sperraatozoids — which  show  us  a  return  to 


186  THE  INDUCTIONS  OP  BIOLOGY. 

unit  life.  Nor,  indeed,  are  we  shown  this  only  in  the  lowest 
plants;  for  it  has  recently  been  found  that  in  certain  of  the 
higher  plants — even  in  Phaenogams — spermatozoids  are  pro- 
duced. That  is  to  say,  the  units  resume  active  lives  at 
places  where  the  controlling  influence  of  the  aggregate  is 
failing;  for,  as  we  shall  hereafter  see,  places  at  which  gene- 
ration commences  answer  to  this  description. 

These  different  kinds  of  evidence  jointly  imply  that  the 
individual  lives  of  the  units  are  subordinate  to  the  general 
life  in  proportion  as  this  is  high.  Where  the  organism  is 
very  inferior  in  type  the  unit-life  remains  permanently  con- 
spicuous. In  some  superior  types  there  is  a  display  of  unit- 
life  during  embryonic  stages  in  which  the  co-ordinating 
action  of  the  aggregate  is  but  incipient.  With  the  advance 
of  development  the  unit-life  diminishes;  but  still,  in  plants, 
recommences  where  the  disintegrating  process  which  initiates 
generation  shows  the  coercive  power  of  the  organization  to 
have  become  small. 

Even  in  the  highest  types,  however,  and  even  when  they 
are  fully  developed,  unit-life  does  not  wholly  disappear :  it  is 
clearly  shown  in  ourselves.  I  do  not  refer  simply  to  the 
fact  that,  as  throughout  the  animal  kingdom  at  large  and  a 
considerable  part  of  the  vegetal  kingdom,  the  male  gene- 
rative elements  are  units  which  have  resumed  the  primitive 
independent  life,  but  I  refer  to  a  much  more  general  fact. 
In  that  part  of  the  organism  which,  being  fundamentally 
an  aqueous  medium,  is  in  so  far  like  the  aqueous  medium  in 
which  ordinary  protozoon  life  is  carried  on,  we  find  an  essen- 
tially protozoon  life.  I  refer  of  course  to  the  blood.  Whether 
the  tendency  of  the  red  corpuscles  (which  are  originally 
developed  from  amoeba-like  cells)  to  aggregate  into  rouleaux 
is  to  be  taken  as  showing  life  in  them,  may  be  left  an  open 
question.  It  suffices  that  the  white  corpuscles  or  leucocytes, 
retaining  the  primitive  amoeboid  character,  exhibit  indi- 
vidual activities :  send  out  prolongations  like  pseudopodia, 
take  in  organic  particles  as  food,  and  are  independently  loco- 


STRUCTURE.  187 

motive.  Though  far  less  numerous  than  the  red  corpuscles, 
yet,  as  ten  thousand  are  contained  in  a  cubic  millimetre  of 
blood — a  mass  less  than  a  pin's  head — it  results  that  the 
human  body  is  pervaded  throughout  all  its  blood-vessels  by 
billions  of  these  separately  living  units.  In  the  lymph,  too, 
which  also  fulfils  the  requirements  of  liquidity,  these  amoeboid 
units  are  found.  Then  we  have  the  curious  transitional 
stage  in  which  units  partially  imbedded  and  partially  free 
display  a  partial  unit-life.  These  are  the  ciliated  epithelium- 
cells,  lining  the  air-passages  and  covering  sundry  of  the  mucous 
membranes  which  have  more  remote  connexions  with  the 
environment,  and  covering  also  the  lining  membranes  of 
certain  main  canals  and  chambers  in  the  nervous  system. 
The  inner  parts  of  these  unite  with  their  fellows  to  form  an 
epithelium,  and  the  outer  parts  of  them,  immersed  either  in 
liquid  or  semi-liquid  (mucus),  bear  cilia  that  are  in  constant 
motion  and  "  produce  a  current  of  fluid  over  the  surface  they 
cover : "  thus  simulating  in  their  positions  and  actions  the 
cells  lining  the  passages  ramifying  through  a  sponge.  The 
partially  independent  lives  of  these,  units  is  further  seen  in 
the  fact  that  after  being  detached  they  swim  about  in  water 
for  a  time  by  the  aid  of  their  cilia, 

§  5±d.  But  in  the  Metazoa  and  Metaphyta  at  large,  the 
associated  units  are,  with  the  exceptions  just  indicated,  com- 
pletely subordinated.  The  unit-life  is  so  far  lost  in  the 
aggregate  life  that  neither  locomotion  nor  the  relative  motion 
of  parts  remains;  and  neither  in  shape  nor  composition  is 
there  resemblance  to  protozoa.  Though  in  many  cases  the 
internal  protoplasm  continues  to  carry  on  vital  processes 
subserving  the  needs  of  the  aggregate,  in  others  vital  processes 
of  an  independent  kind  appear  to  cease. 

It  will  naturally  be  supposed  that  after  recognizing 'this 
fundamental  trait  common  to  all  types  of  organisms  above 
the  Protozoa  and  Protopliyta,  the  next  step  in  an  account  of 
structure  must  be  a  description  of  their  organs,  variously 


188  THE  INDUCTIONS  OF  BIOLOGY, 

formed  and  combined — if  not  in  detail  yet  in  their  general 
characters.  This,  however,  is  an  error.  There  are  certain 
truths  of  structure  higher  in  generality  than  any  which  can 
be  alleged  of  organs.  We  shall  see  this  if  we  compare  organs 
with  one  another. 

Here  is  a  finger  stiffened  by  its  small  bones  and  yet  made 
flexible  by  the  uniting  joints.  There  is  a  femur  which  helps 
its  fellow  to  support  the  weight  of  the  body ;  and  there  again 
is  a  rib  which,  along  with  others,  forms  a  protective  box 
for  certain  of  the  viscera.  Dissection  reveals  a  set  of  muscles 
serving  to  straighten  and  bend  the  fingers,  certain  other 
muscles  that  move  the  legs,  and  some  inconspicuous  muscles 
which,  contracting  every  two  or  three  seconds,  slightly  raise 
the  ribs  and  aid  in  inflating  the  lungs.  That  is  to  say, 
fingers,  legs,  and  chest  possess  certain  structures  in  common. 
There  is  in  each  case  a  dense  substance  capable  of  resisting 
stress  and  a  contractile  substance  capable  of  moving  the 
dense  substance  to  which  it  is  attached.  Hence,  then,  we 
have  first  to  give  an  account  of  these  and  other  chief  ele- 
ments which,  variously  joined  together,  form  the  different 
organs :  we  have  to  observe  the  general  characters  of  tissues. 

On  going  back  to  the  time  when  the  organism  begins  with 
a  single  cell,  then  becomes  a  spherical  cluster  of  cells,  and 
then  exhibits  differences  in  the  modes  of  aggregation  of  these 
cells,  the  first  conspicuous  rise  of  structure  (limiting  our- 
selves to  animals)  is  the  formation  of  three  layers.  Of  these 
the  first  is,  at  the  outset  and  always,  the  superficial  layer  in 
direct  contact  with  the  environment.  The  second,  being  origi- 
nally a  part  of  the  first,  is  also  in  primitive  types  in  con- 
tact with  the  environment,  but,  being  presently  intro- 
verted, forms  the  rudiment  of  the  food-cavity;  or,  otherwise 
arising  in  higher  types,  is  in  contact  with  the  yelk  or  food 
provided  by  the  parent.  And  the  third,  presently  formed 
between  these  two,  consists  at  the  outset  of  cells  derived 
from  them  imbedded  in  an  intercellular  substance  of  jelly- 
like  consistence,  Hence  originate  the  great  groups  classed 
as  epithelium-ti|gue4  Connective  tissue  (including  osseous,  tis* 


STRUCTURE.  ISO 

sue),  muscular  tissue,  nervous  tissue.  These  severally  con- 
tain sub-kinds,  each  of  which  is  a  complex  of  differentiated 
cells.  Being  brief,  and  therefore  fitted  for  the  present  pur- 
poses, the  sub-classification  given  by  Prof.  R.  Hertwig  may 
here  be  quoted ; — 

"The  physiological  character  of  epithelia  is  given  in  the  fact  that 
they  cover  the  surfaces  of  the  body,  their  morphological  character  in 
that  they  consist  of  closely  compressed  cells  united  only  by  a  cement- 
ing substance. 

"According  to  their  further  functional  character  epithelia  are 
divided  into  glandular  epithelia  (unicellular  and  multicellular  glands), 
sensory,  germinal,  and  pavement  epithelia. 

"  According  to  the  structure  are  distinguished  one-layered  (cubical, 
cylindrical,  pavement  epithelia)  and  many-layered  epithelia,  ciliated 
and  flagellated  epithelia,  epithelia  with  or  without  cuticle. 

"The  physiological  character  of  the  connective  tissues  rests  upon 
the  fact  that  they  fill  up  spaces  between  other  tissues  in  the  interior 
of  the  body. 

"The  morphological  character  depends  upon  the  presence  of  the 
intercellular  substance. 

"According  to  the  quantity  and  the  structure  of  the  intercellular 
substance  the  connective  substances  are  divided  into  (1)  cellular  (with 
little  intercellular  substance);  (2)  homogeneous;  (3)  fibrillar  connec- 
tive tissue ;  (4)  cartilage ;  (5)  bone. 

"The  physiological  character  of  muscular  tissue  is  contained  in 
the  increased  capacity  for  contraction. 

"The  morphological  character  is  found  in  the  fact  that  the  cells 
have  secreted  muscle-substance. 

"  According  to  the  nature  of  the  muscle-substance  are  distinguished 
smooth  and  cross-striated  muscle-fibres. 

"According  to  the  character  and  derivation  of  the  cells  (muscle- 
corpuscles)  the  musculature  is  divided  into  epithelial  (epithelial  mus- 
cle-cells, primary  bundles)  and  connective-tissue  muscle  cells  (con- 
tractile fibre-cells). 

"The  physiological  character  of  nervous  tissue  rests  upon  the 
transmission  of  sensory  stimuli  and  voluntary  impulses,  and  upon  the 
co  ordination  of  these  into  unified  psychic  activity. 

"The  conduction  takes  place  by  means  of  nerve-fibres  (non- 
medullated  and  medullated  fibrils  and  bundles  of  fibrils);  the  co- 
ordination of  stimuli  by  means  of  ganglion-cells  (bipolar,  multipolar 
ganglion-cells),"  (General Principles qf  Zoology \  pp,  117-9.) 


190  THE  INDUCTIONS  OF  BIOLOGY. 

But  now  concerning  cells  out  of  which,  variously  modified, 
obscured,  and  sometimes  obliterated,  tissues  are  formed,  we 
have  to  note  a  fact  of  much  significance.  Along  with  the 
cell-doctrine  as  at  first  held,  when  'attention  was  given  to 
the  cell  itself  rather  than  to  its  contents,  there  went  the 
belief  that  each  of  these  morphological  units  is  structu- 
rally separate  from  its  neighbours.  But  since  establishment 
of  the  modern  view  that  the  essential  element  is  the  con- 
tained protoplasm,  histologists  have  discovered  that  there 
are  protoplasmic  connexions  between  the  contents  of  adjacent 
cells.  Though  cursorily  observed  at  earlier  dates,  it  was  not 
until  some  twenty  years  ago  that  in  plant-tissues  these  were 
clearly  shown  to  pass  through  openings  in  the  cell-walls.  It 
is  said  that  in  some  cases  the  openings  are  made,  and  the 
junctions  established,  by  a  secondary  process ;  but  the  impli- 
cation is  that  usually  these  living  links  are  left  between 
multiplying  protoplasts;  so  that  from  the  outset  the  proto- 
plasm pervading  the  whole  plant  maintains  its  continuity. 
More  recently  sundry  zoologists  have  alleged  that  a  like  con- 
tinuity exists  in  animals.  Especially  has  this  been  main- 
tained by  Mr.  Adam  Sedgwick.  Numerous  observations  made 
on  developing  ova  of  fishes  have  led  him  to  assert  that  in  no 
case  do  the  multiplying  cells  so-called — blastomeres  and 
their  progeny — become  entirely  separate.  Their  fission  is  in 
all  cases  incomplete.  A  like  continuity  has  been  found  in 
the  embryos  of  many  Arthropods,  and  more  recently  in  the 
segmenting  eggs  and  blastulae  of  Echinoderms.  The  syn- 
cytium  thus  formed  is  held  by  Mr.  Sedgwick  to  be  main- 
tained in  adult  life,  and  in  this  belief  he  is  in  agreement 
with  sundry  others.  Bridges  of  protoplasm  have  been  seen 
between  epithelium-cells,  and  it  is  maintained  that  cartilage- 
cells,  connective  tissue  cells,  the  cells  forming  muscle-fibres, 
as  well  as  nerve-cells,  have  protoplasmic  unions.  Nay,  some 
even  assert  that  an  ovum  preserves  a  protoplasmic  connexion 
with  the  matrix  in  which  it  develops. 

A  corollary  of  great  significance  may  here  be  drawn.     It 


STRUCTURE.  191 

has  been  observed  that  within  a  vegetal  cell  the  strands  of 
protoplasm  stretched  in  this  or  that  direction  contain  moving 
granules,  showing  that  the  strands  carry  currents.  It  has 
also  been  observed  that  when  the  fission  of  a  protozoon  is  so 
nearly  complete  that  its  two  halves  remain  connected  only 
by  a  thread,  currents  of  protoplasm  move  through  this 
thread,  now  one  way  now  the  other.  The  inference  fairly  to 
be  drawn  is  that  such  currents  pass  also  through  the  strands 
which  unite  the  protoplasts  forming  a  tissue.  What  must 
happen?  So  long  as  adjacent  cells  with  their  contents  are 
subject  to  equal  pressures  no  tendency  to  redistribution  of 
the  protoplasm  exists,  and  there  may  then  occur  the  action 
sometimes  observed  inside  the  strands  within  a  cell:  cur- 
rents with  their  contained  granules  moving  in  opposite  direc- 
tions. But  if  the  cells  forming  a  portion  of  tissue  are  subject 
to  greater  pressure  than  the  cells  around,  their  contained 
protoplasm  must  be  forced  through  the  connecting  threads 
into  these  surrounding  cells.  Every  change  of  pressure  at 
every  point  must  cause  movements  and  counter-movements 
of  this  kind.  Now  in  the  Metazoa  at  large,  or  at  least  in  all 
exhibiting  relative  motions  of  parts,  and  especially  in  all 
which  arc  capable  of  rapid  locomotion,  such  changes  of 
pressure  are  everywhere  and  always  taking  place.  The 
contraction  of  a  muscle,  besides  compressing  its  components, 
compresses  neighbouring  tissues;  and  every  instant  contrac- 
tions and  relaxations  of  muscles  go  on  throughout  the 
limbs  and  body  during  active  exertion.  Moreover,  each  atti- 
tude— standing,  sitting,  lying  down,  turning  over — entails  a 
different  set  of  pressures,  both  of  the  parts  on  one  another 
and  on  the  ground;  and  those  partial  arrests  of  motion 
which  result  from  sitting  down  the  feet  alternately  when 
running,  send  jolts  or  waves  of  varying  pressure  through  the 
body.  The  vital  actions,  too,  have  kindred  effects.  An  in- 
spiration alters  the  stress  on  the  tissues  throughout  a  con- 
siderable part  of  the  trunk,  and  a  heart-beat  propels,  down  to 
the  smallest  arteries,  waves  which  slightly  strain  the  tissues 


192  THE  INDUCTIONS  OP  BIOLOGY. 

at  large.  The  component  cells,  thus  subject  to  mechanical 
disturbances,  small  and  great,  perpetual  and  occasional,  are 
ever  having  protoplasm  forced  into  them  and  forced  out  of 
them.  There  are  gurgitations  and  regurgitations  which,  if 
they  do  not  constitute  a  circulation  properly  so  called,  at 
least  imply  an  unceasing  redistribution.  And  the  implica- 
tion is  that  in  the  course  of  days,  weeks,  months,  years,  each 
portion  of  protoplasm  visits'  every  part  of  the  body. 

Without  here  stating  specifically  the  bearings  of  these 
inferences  upon  the  problems  of  heredity,  it  will  be  manifest 
that  certain  difficulties  they  present  are  in  a  considerable 
degree  diminished. 

§  54e.  Returning  from  this  parenthetical  discussion  to 
the  subject  of  structure,  we  have  to  observe  that  besides 
facts  presented  by  tissues  and  facts  presented  by  organs, 
there  are  certain  facts,  less  general  than  the  one  and  more 
general  than  the  other,  which  must  now  be  noted.  In  the 
order  of  decreasing  generality  an  account  of  organs  should 
be  preceded  by  an  account  of  systems  of  organs.  Some  of 
these,  as  the  muscular  system  and  the  osseous  system,  are 
co-extensive  with  tissues,  but  others  of  them  are  not.  The 
nervous  system,  for  example,  contains  more  than  one  kind  of 
tissue  and  is  constituted  of  many  different  structures :  be- 
sides afferent  and  efferent  nerves  there  are  the  ganglia  im- 
mediately controlling  the  viscera,  and  there  are  the  spinal 
and  cerebral  masses,  the  last  of  which  is  divisible  into 
numerous  unlike  parts.  Then  we  have  the  vascular  system 
made  up  of  the  heart,  arteries,  veins,  and  capillaries.  The 
lymphatic  system,  too,  with  its  scattered  glands  and  ramify- 
ing channels  has  to  be  named.  And  then,  not  forgetting  the 
respiratory  system  with  its  ancillary  appliances,  we  have  the 
highly  heterogeneous  alimentary  system;  including  a  great 
number  of  variously-constructed  organs  which  work  together. 
On  contemplating  these  systems  we  see  their  common 
character  to  be  that  while  as,  wholes,  they  cooperate  for  the 


STRUCTURE.  193 

carrying  on  of  the  total  life,  each  of  them  consists  of  co- 
operative parts :  there  is  cooperation  within  cooperation. 

There  is  another  general  aspect  under  which  structures 
must  be  contemplated.  They  are  divisible  into  the  universal 
and  the  particular — those  which  are  everywhere  present 
and  those  which  occupy  special  places.  The  blood  which  a 
scratch  brings  out  shows  us  that  the  vascular  system  sends 
branches  into  each  spot.  The  sensation  accoinpanying  a 
scratch  proves  that  the  nervous  system,  too,  has  there  some 
of  its  ultimate  fibrils.  Unobtrusive,  and  yet  to  be  found  at 
(•very  point,  are  the  ducts  of  the  lymphatic  system.  And  in 
all  parts  exists  the  connective  tissue — an  inert  tough  sub- 
stance which,  running  through  interspaces,  wraps  up  and 
binds  together  the  other  tissues.  As  is  implied  by  this  de- 
scription, these  structures  stand  in  contrast  with  local 
structures.  Here  is  a  bone,  there  is  a  muscle,  in  this  place 
a  gland,  in  that  a  sense-organ.  Each  has  a  limited  extent 
and  a  particular  duty.  But  through  every  one  of  them  ramify 
branches  of  these  universal  structures.  Every  one  of  them 
has  its  arteries  and  veins  and  capillaries,  its  nerves,  its  lym- 
phatics, its  connective  tissue. 

Eecognition  of  this  truth  introduces  what  little  has  here 
to  be  said  concerning  organs ;  for  of  course  in  a  work  limited 
to  principles  no  detailed  account  of  these  can  be  entered 
upon.  This  remainder  truth  is  that,  different  as  they  may 
be  in  the  rest  of  their  structures,  all  organs  are  alike  in  certain 
of  their  structures.  All  are  furnished  with  these  appliances 
for  nutrition,  depuration  and  excitation :  they  have  all  to  be 
sustained,  all  to  be  stimulated,  all  to  be  kept  clean.  It  has 
finally  to  be  remarked  that  the  general  structures  which 
pervade  all  the  special  structures  at  the  same  time  per- 
vade one  another.  The  universal  nervous  system  has  every- 
where ramifying  through  it  the  universal  vascular  system 
which  feeds  it;  and  the  universal  vascular  system  is  fol- 
lowed throughout  all  its  ramifications  by  special  nerves 
which  control  it.  The  lymphatics  forming  a  drainage- 


194  THE  INDUCTIONS  OF  BIOLOGY. 

system  run  throughout  the  other  systems;  and  in  each  of 
these  universal  systems  is  present  the  connective  tissue  hold- 
ing their  parts  in  position. 

§  54/.  So  vast  and  varied  a  subject  as  organic  structure, 
even  though  the  treatment  of  it  is  limited  to  the  enuncia- 
tion of  principles,  cannot,  of  course,  be  dealt  with  in  the  space 
here  assigned.  Next  to  nothing  has  been  said  about  plant- 
structures,  and  in  setting  forth  the  leading  traits  of  animal- 
structures  the  illustrations  given  have  been  mostly  taken  from 
highly-developed  creatures.  In  large  measure  adumbration 
rathef  than  exposition  is  the  descriptive  word  to  be  applied. 

Nevertheless  the  reader  may  carry  away  certain  truths 
which,  exemplified  in  a  few  cases,  are  exemplified  more  or 
less  fully  in  all  cases.  There  is  the  fundamental  fact  that 
the  plants  and  animals  with  which  we  are  familiar — Meta- 
pliyta  and  Metazoa — are  formed  by  the  aggregation  of  units 
homologous  with  Protozoa.  These  units,  often  conspicuously 
showing  their  homology  in  early  embryonic  stages,  continue 
some  of  them  to  show  it  throughout  the  lives  of  the  highest 
type  of  Metazoa,  which  contain  billions  of  units  carrying  on 
a  protozoon  life.  Of  the  protoplasts  not  thus  active  the 
great  mass,  comparatively  little  transformed  in  low  organ- 
isms, become  more  and  more  transformed  as  the  ascent  to 
high  organisms  goes  on ;  so  that,  undergoing  numerous  kinds 
of  metamorphoses,  they  lose  all  likeness  to  their  free  homo- 
logues,  both  in  shape  and  composition.  The  cell-contained 
protoplasts  thus  variously  changed  are  fused  together  into 
tissues  in  which  their  individualities  are  practically  lost ;  but 
they  nevertheless  remain  connected  throughout  by  permeable 
strands  of  protoplasm.  Arising  by  complication  of  the  outer 
and  inner  layers  of  the  embryo  and  growing  more  unlike 
as  their  units  become  more  obscured,  these  tissues  are  formed 
into  systems,  which  develop  into  sets  of  organs.  Some  of 
the  resulting  structures  are  localized  and  special  but  others 
are  everywhere  interfused. 


STRUCTURE.  195 

While  the  first  named  of  these  facts  are  displayed  in 
every  Metazoon,  and  while  the  last  named  are  visible  only 
in  Metazoa  of  considerably  developed  structures,  a  gradual 
transition  is  shown  in  intermediate  kinds  of  Metazoa.  Of 
this  transition  it  remains  to  say  that  it  is  effected  by  the 
progressive  development  of  auxiliary  appliances.  For 
example,  the  primitive  foot-cavity  is  a  sac  with  one  opening 
only;  then  comes  a  second  opening  through  which  the 
waste-matter  of  the  food  is  expelled.  The  alimentary  canal 
between  these  openings  is  at  first  practically  uniform;  after- 
wards in  a  certain  part  of  its  wall  arise  numerous  bile-cells; 
these  accumulating  form  a  hollow  prominence;  and  this, 
enlarging,  becomes  in  higher  types  a  liver,  while  the  hollow 
becomes  its  duct.  In  other  gradual  ways  are  formed  other 
appended  glands.  Meanwhile  the  canal  itself  has  its  parts 
differentiated:  one  being  limited  to  swallowing,  another  to 
triturating,  another  to  adding  various  solvents,  another  to 
absorbing  the  prepared  nutriment,  another  to  ejecting  the 
residue.  Take  again  the  visual  organ.  The  earliest  form  of 
it  is  a  mere  pigment-speck  below  the  surface.  From  this 
(saying  nothing  here  of  multiple  eyes)  we  rise  by  successive 
complications  to  a  retina  formed  of  multitudinous  sensory 
elements,  lenses  for  throwing  images  upon  it,  a  curtain  for 
shutting  out  more  or  less  light,  muscles  for  moving  the 
apparatus  about,  others  for  adjusting  its  focus;  and,  finally, 
added  to  these,  either  a  nictitating  membrane  or  eyelids  for 
perpetually  wiping  its  surface,  and  a  set  of  eyelashes  giving 
notice  when  a  foreign  body  is  dangerously  near.  This  process 
of  elaborating  organs  so  as  to  meet  additional  requirements 
by  additional  parts,  is  the  process  pursued  throughout  the 
body  at  large. 

Of  plant-structures,  concerning  which  so  little  has  been 
said,  it  may  here  be  remarked  that  their  relative  simplicity  is 
due  to  the  simplicity  of  their  relations  to  food.  The  food  of 
plants  is  universally  distributed,  while  that  of  animals  is 
dispersed.  The  immediate  consequences  are  that  in  the  one 


196  THE  INDUCTIONS  OF  BIOLOGY. 

case  motion  and  locomotion  are  superfluous,  while  in  the 
other  case  they  are  necessary:  the  differences  in  the  degrees 
of  structure  being  consequences.  Recognizing  the  locomo- 
tive powers  of  minute  Algce  and  the  motions  of  such  other 
Algce  as  Oscillatoria,  as  well  as  those  movements  of  leaves 
and  fructifying  organs  seen  in  some  Phaenogams,  we  may  say, 
generally,  that  plants  are  motionless;  but  that  they  can 
nevertheless  carry  on  their  lives  because  they  are  bathed  by 
the  required  nutriment  in  the  air  and  in  the  soil.  Contrari- 
wise, the  nutriment  animals  require  is  distributed  through 
space  in  portions:  in  some  cases  near  one  another  and  in 
other  cases  wide  apart.  Hence  motion  and  locomotion  are 
necessitated;  and  the  implication  is  that  animals  must  have 
organs  which  render  them  possible.  In  the  first  place  there 
must  be  either  limbs  or  such  structures  as  those  which  in 
fish,  snakes,  and  worms  move  the  body  along.  In  the  second 
place,  since  action  implies  waste,  there  must  be  a  set  of 
channels  to  bring  repairing  materials  to  the  moving  parts. 
In  the  third  place  there  must  be  an  alimentary  system  for 
taking  in  and  preparing  these  materials.  In  the  fourth 
place  there  must  be  organs  for  separating  and  excreting 
waste-products.  All  these  appliances  must  be  more  highly 
developed  in  proportion  as  the  required  activity  is  greater. 
Then  there  must  be  an  apparatus  for  directing  the  motions 
and  locomotions — a  nervous  system;  and  as  fast  as  these 
become  rapid  and  complex  the  nervous  system  must  be 
largely  developed,  ending  in  great  nervous  centres — seats  of 
intelligence  by  which  the  activities  at  large  are  regulated. 
Lastly,  underlying  all  the  structural  contrasts  between  plants 
and  animals  thus  originating,  there  is  the  chemical  contrast; 
since  the  necessity  for  that  highly  nitrogenous  matter  of 
which  animals  are  formed,  is  entailed  by  the  necessity  for 
rapidly  evolving  the  energy  producing  motion.  So  that, 
strange  as  it  seems,  those  chemical,  physical,  and  mental 
characters  of  animals  which  so  profoundly  distinguish  them 
from  plants,  are  all  remote  results  of  the  circumstance  that 
their  food  is  dispersed  instead  of  being  everywhere  present. 


CHAPTER  III. 

FUNCTION. 

§  55.  DOES  Structure  originate  Function,  or  does  Func- 
tion originate  Structure  ?  is  a  question  about  which  there  has 
been  disagreement.  Using  the  word  Function  in  its  widest 
signification,  as  the  totality  of  all  vital  actions,  the  question 
amounts  to  this — does  Life  produce  Organization,  or  does 
Organization  produce  Life  ? 

To  answer  this  question  is  not  easy,  since  we  habitually 
find  the  two  so  associated  that  neither  seems  possible  without 
the  other;  and  they  appear  uniformly  to  increase  and  de- 
crease together.  If  it  be. said  that  the  arrangement  of  or- 
ganic substances  in  particular  forms,  cannot  be  the  ultimate 
cause  of  vital  changes,  which  must  depend  on  the  properties 
of  such  substances;  it  may  be  replied  that,  in  the  absence  of 
structural  arrangements,  the  forces  evolved  cannot  be  so 
directed  and  combined  as  to  secure  that  correspondence  be- 
tween inner  and  outer  actions  which  constitutes  Life.  Again, 
to  the  allegation  that  the  vital  activity  of  every  germ  whence 
an  organism  arises,  is  obviously  antecedent  to  the  develop- 
ment of  its  structures,  there  is  the  answer  that  such  germ 
is  not  absolutely  structureless. 

But  in  truth  this  question  is  not  determinable  by  any 

evidence  now  accessible  to  us.     The  very  simplest  forms  of 

life  known  (even  the  non-nucleated,  if  there  are  any)  consist 

of  granulated  protoplasm ;  and  granulation  implies  structure. 

U  197 


198  THE  INDUCTIONS  OP  BIOLOGY. 

Moreover  since  each  kind  of  protozoon,  even  the  lowest,  has 
its  specific  mode  of  development  and  specific  activity — even 
down  to  bacteria,  some  kinds  of  which,  otherwise  indistin- 
guishable, are  distinguishable  by  their  different  reactions  on 
their  media — we  are  obliged  to  conclude  that  there  must  be 
constitutional  differences  between  the  protoplasms  they  con- 
sist of,  and  this  implies  structural  differences.  It  seems  that 
structure  and  function  must  have  advanced  pari  passu: 
some  difference  of  function,  primarily  determined  by  some 
difference  of  relation  to  the  environment,  initiating  a  slight 
difference  of  structure,  and  this  again  leading  to  a  more  pro- 
nounced difference  of  function ;  and  so  on  through  continuous 
actions  and  reactions. 

§  56.  Function  falls  into  divisions  of  several  kinds  ac- 
cording to  our  point  of  view.  Let  us  take  these  divisions  in 
the  order  of  their  simplicity. 

Under  Function  in  its  widest  sense,  are  included  both  the 
statical  and  the  dynamical  distributions  of  force  which  an 
organism  opposes  to  the  forces  brought  to  bear  on  it.  In  a 
tree  the  woody  core  of  trunk  and  branches,  and  in  an  animal 
the  skeleton,  internal  or  external,  may  be  regarded  as  pas- 
sively resisting  the  gravity  and  momentum  which  tend 
habitually  or  occasionally  to  derange  the  requisite  relations 
between  the  organism  and  its  environment;  and  since  they 
resist  these  forces  simply  by  their  cohesion,  their  functions 
may  be  classed  as  statical.  Conversely,  the  leaves  and  sap- 
vessels  in  a  tree,  and  those  organs  which  in  an  animal 
similarly  carry  on  nutrition  and  circulation,  as  well  as  those 
which  generate  and  direct  muscular  motion,  must  be  con- 
sidered as  dynamical  in  their  actions.  From  another 
point  of  view  Function  is  divisible  into  the  accumulation  of 
energy  (latent  in  food) ;  the  expenditure  of  energy  (latent  in 
the  tissues  and  certain  matters  absorbed  by  them) ;  and  the 
transfer  of  energy  (latent,  in  the  prepared  nutriment  or  blood) 
from  the  parts  which  accumulate  to  the  parts  whrch  expend. 


FUNCTION.  199 

In  plants  we  see  little  beyond  the  first  of  these :  expenditure 
being  comparatively  slight,  and  transfer  required  mainly  to 
facilitate  accumulation/  In  animals  the  function  of  accumu- 
lation comprehends  those  processes  by  which  the  materials 
containing  latent  energy  are  taken  in,  digested,  and  separated 
from  other  materials;  the  function  of  transfer  comprehends 
those  processes  by  which  these  materials,  and  such  others  as 
are  needful  to  liberate  the  energies  they  contain,  are  con- 
veyed throughout  the  organism;  and 'the  function  of  expendi- 
ture comprehends  those  processes  by  which  the  energy  is 
liberated  from  these  materials  and  transformed  into  properly 
co-ordinated  motions.  Each  of  these  three  most  gene- 

ral divisions  includes  several  more  special  divisions.  The 
accumulation  of  energy  may  be  separated  into  alimentation 
and  aeration;  of  which  the  first  is  again  separable  into  the 
various  acts  gone  through  between  prehension  of  food  and 
the  transformation  of  part  of  it  into  blood.  By  the  transfer 
of  energy  is  to  be  understood  what  we  call  circulation;  if  the 
meaning  of  circulation  be  extended  to  embrace  the  duties  of 
both  the  vascular  system  and  the  lymphatics.  Under  the 
head  of  expenditure  of  energy  come  nervous  actions  and 
muscular  actions:  though  not  absolutely  co-extensive  with 
expenditure  these  are  almost  so.  Lastly,  there  are  the 
subsidiary  functions  which  do  not  properly  fall  within  any 
of  these  general  functions,  but  subserve  them  by  removing 
the  obstacles  to  their  performance:  those,  namely,  of  ex- 
cretion and  exhalation,  whereby  waste  products  are  got 
rid  of.  Again,  disregarding  their  purposes  and 

considering  them  analytically,  the  general  physiologist  may 
consider  functions  in  their  widest  sense  as  the  correlatives  of 
tissues — the  actions  of  epidermic  tissue,  cartilaginous  tissue, 
elastic  tissue,  connective  tissue,  osseous  tissue,  muscular 
tissue,  nervous  tissue,  glandular  tissue.  Once  more, 

physiology  in  its  concrete  interpretations  recognizes  special 
functions  as  the  ends  of  special  organs — regards  the  teeth  as 
having  the  office  of  mastication;  the  heart  as  an  apparatus 


200  THE  INDUCTIONS  OP  BIOLOGY. 

to  propel  blood;  this  gland  as  fitted  to  produce  one  requisite 
secretion  and  that  to  produce  another;  each  muscle  as  the 
agent  of  a  particular  motion;  each  nerve  as  the  vehicle  of  a 
special  sensation  or  a  special  motor  impulse. 

It  is  clear  that  dealing  with  Biology  only  in  its  larger 
aspects,  specialities  of  function  do  not  concern  us;  except  in 
so  far  as  they  serve  to  illustrate,  or  to  qualify,  its  generalities. 

§  57.  The  first  induction  to  be  here  set  down  is  a  familiar 
and  obvious  one;  the  induction,  namely,  that  complexity  of 
function  is  the  correlative  of  complexity  of  structure.  The 
leading  aspects  of  this  truth  must  be  briefly  noted. 

Where  there  are  no  distinctions  of  structure  there  are  no 
distinctions  of  function.  A  Khizopod  will  serve  as  an  illus- 
tration. From  the  outside  of  this  creature,  which  has  not 
even  a  limiting  membrane,  there  are  protruded  numerous 
processes.  Originating  from  any  point  of  the  surface,  each  of 
these  may  contract  again  and  disappear,  or  it  may  touch 
some  fragment  of  nutriment  which  it  draws  with  ity  when 
contracting,  into  the  general  mass — thus  serving  as  hand  and 
mouth;  or  it  may  come  in  contact  with  its  fellow-processes 
at  a  distance  from  the  body  and  become  confluent  with  them ; 
or  it  may  attach  itself  to  an  adjacent  fixed  object,  and  help 
by  its  contraction  to  draw  the  body  into  a  new  position.  In 
brief,  this  speck  of  animated  jelly  is  at  once  all  stomach,  all 
skin,  all  mouth,  all  limb,  and  doubtless,  too,  all  lung.  In 

organisms  having  a  fixed  distribution  of  parts  there  is  a  con- 
comitant fixed  distribution  of  actions.  Among  plants  we  see 
that  when,  instead  of  a  uniform  tissue  like  that  of  many 
Algce,  everywhere  devoted  to  the  same  process  of  assimilation, 
there  arise,  as  in  the  higher  plants,  root  and  stem  and  leaves, 
there  arise  correspondingly  unlike  processes.  Still  more  con- 
spicuously among  animals  do  there  result  varieties  of  function 
when  the  originally  homogeneous  mass  is  replaced  by  hetero- 
geneous organs ;  since,  both  singly  and  by  their  combinations, 
modified  parts  generate  modified  changes.  Up  to  the 


FUNCTION.  201 

highest  organic  types  this  dependence  continues  manifest; 
and  it  may  be  traced  not  only  under  this  most  general  form, 
but  also  under  the  more  special  form  that  in  animals  having 
one  set  of  functions  developed  to  more  than  usual  hetero- 
geneity there  is  a  correspondingly  heterogeneous  apparatus 
devoted  to  them.  Thus  among  birds,  which  have  more  varied 
locomotive  powers  than  mammals,  the  limbs  are  more  widely 
differentiated ;  while  the  higher  mammals,  which  rise  to  more 
numerous  and  more  involved  adjustments  of  inner  to  outer 
relations  than  birds,  have  more  complex  nervous  systems. 

§  58.  It  is  a  generalization  almost  equally  obvious  with 
the  last,  that  functions,  like  structures,  arise  by  progressive 
differentiations.  Just  as  an  organ  is  first  an  indefinite  rudi- 
ment, having  nothing  but  some  most  general  characteristic 
in  common  with  the  form  it  is  ultimately  to  take;  so  a 
function  begins  as  a  kind  of  action  that  is  like  the  kind  of 
action  it  will  eventually  become,  only  in  a  very  vague  way. 
And  in  functional  development.,  as  in  structural  development, 
the  leading  trait  thus  early  manifested  is  followed  succes- 
sively by  traits  of  less  and  less  importance.  This  holds 
equally  throughout  the  ascending  grades  of  organisms  and 
throughout  the  stages  of  each  organism.  Let  us  look  at 
cases:  confining  our  attention  to  animals,  in  which  func- 
tional development  is  better  displayed  than  in  plants. 

The  first  differentiation  established  separates  the  two 
fundamentally-opposed  functions  above  named — the  accumu- 
lation of  energy  and  the  expenditure  of  energy.  Passing  over 
the  Protozoa  (among  which,  however,  such  tribes  as  present 
fixed  distributions  of  parts  show  us  substantially  the  same 
tiling),  and  commencing  with  the  lowest  Ccelenterata,  where 
definite  tissues  make  their  appearance,,  we  observe  that  the 
only  large  functional  distinction  is  between  the  endoderm, 
which  absorbs  nutriment,  and  the  ectoderm  which,  by  its 
own  contractions  and  those  of  the  tentacles  it  bears,  produces 
motion:  the  contractility  being  however  to  some  extent 


202  THE  INDUCTIONS  OP  BIOLOGY. 

shared  by  the  endoderm.  That  the  functions  of  accumulation 
and  expenditure  are  here  very  incompletely  distinguished, 
may  be  admitted  without  affecting  the  position  that  this  is 
the  first  specialization  which  begins  to  appear.  These 

two  most  genera^  and  most  radically-opposed  functions 
become  in  the  Polyzoa,  much  more  clearly  marked-off  from 
each  other:  at  the  same  time  that  each  of  them  becomes 
partially  divided  into  subordinate  functions.  The  endoderm 
and  ectoderm  are  no  longer  merely  the  inner  and  outer  walls 
of  the  same  simple  sac  into  which  the  food  is  drawn:  but  the 
endoderm  forms  a  true  alimentary  canal,  separated  from  the 
ectoderm  by  a  peri-visceral  cavity,  containing  the  nutritive 
matters  absorbed  from  the  food.  That  is  to  say,  the  function 
of  accumulating  force  is  exercised  by  a  part  distinctly  divided 
from  the  part  mainly  occupied  in  expending  force:  the 
structure  between  them,  full  of  absorbed  nutriment,  effecting 
in  a  vague  way  that  transfer  of  force  which,  at  a  higher  stage 
of  evolution,  becomes  a  third  leading  function.  Meanwhile, 
the  endoderm  no  longer  discharges  the  accumulative  func- 
tion in  the  same  way  throughout  its  whole  extent;  but  its 
different  portions,  oesophagus,  stomach  and  intestine,  perform 
different  portions  of  this  function.  And  instead  of  a 
contractility  uniformly  diffused  through  the  ectoderm,  there 
have  arisen  in  the  intermediate  mesoderm  some  parts  which 
have  the  office  of  contracting  (muscles),  and  some  parts 
which  have  the  office  of  making  them  contract  (nerves  and 
ganglia).  As  we  pass  upwards,  the  transfer  of  force, 

hitherto  effected  quite  incidentally,  comes  to  have  a  special 
organ.  In  the  ascidian,  circulation  is  produced  by  a  muscular 
tube,  open  at  both  ends,  which,  by  a  wave  of  contraction 
passing  along  it,  sends  out  at  one  end  the  nutrient  fluid 
drawn  in  at  the  other;  and  which,  having  thus  propelled 
the  fluid  for  a  time  in  one  direction,  reverses  its  movement 
and  propels  it  in  the  opposite  direction.  By  such  means 
does  this  rudimentary  heart  generate  alternating  currents  in 
the  nutriment  occupying  the  peri-visceral  cavity.  How  the 


FUNCTION.  203 

function  of  transferring  energy,  thus  vaguely  indicated  in 
these  inferior  forms,  comes  afterwards  to  be  the  definitely- 
separated  office  of  a  complicated  apparatus  made  up  of  many 
parts,  each  of  which  has  a  particular  portion  of  the  general 
duty,  need  not  be  described.  It  is  sufficiently  manifest  that 
this  general  function  becomes  more  clearly  marked-off  from 
the  others,  at  the  same  time  that  it  becomes  itself  parted 
into  subordinate  functions. 

•  In  a  developing  embryo,  the  functions  or  more  strictly 
the  structures  which  are  to  perform  them,  arise  in  the  same 
general  order.  A  like  primary  distinction  very  early  appears 
between  the  endoderm  and  the  ectoderm — the  part  which 
has  the  office  of  accumulating  energy,  and  the  part  out  of 
which  grow  those  organs  that  are  the  great  expenders  of 
energy.  Between  these  two  there  presently  arises  the  meso- 
derm  in  which  becomes  visible  the  rudiment  of  that  vascular 
system,  which  has  to  fulfil  the  intermediate  duty  of  trans- 
ferring energy.  Of  these  three  general  functions,  that  of 
accumulating  energy  is  carried  on  from  the  outset:  the 
endoderm,  even  while  yet  incompletely  differentiated  from 
the  ectoderm,  absorbs  nutritive  matters  from  the  subjacent 
yelk.  The  transfer  of  energy  is  also  to  some  extent  effected 
by  the  rudimentary  vascular1  system,  as  soon  as  its  central 
cavity  and  attached  vessels  are  sketched  out.  But  the  ex- 
penditure of  energy  (in  the  higher  animals  at  least)  is  not 
appreciably  displayed  by  those  ectodermic  and  mesodermic 
structures  that  are  afterwards  to  be  mainly  devoted  to  it: 
there  is  no  sphere  for  the  actions  of  these  parts.  Simi- 

larly with  the  chief  subdivisions  of  these  fundamental  func- 
tions. The  distinction  first  established  separates  the  office 
of  transforming  other  energy  into  mechanical  motion,  from 
the  office  of  liberating  the  energy  to  be  so  transformed. 
While  in  the  layer  between  endoderm  and  ectoderm  are 
arising  the  rudiments  of  the  muscular  system,  there  is  marked 
out  in  the  ectoderm  the  rudiment  of  the  nervous  system. 
This  indication  of  structures  which  are  to  share  between 


204  THE  INDUCTIONS  OF  BIOLOGY. 

them  the  general  duty  of  expending  energy,  is  soon  followed  by 
changes  that  foreshadow  further  specializations  of  this  general 
duty.  In  the  incipient  nervous  system  there  begins  to  arise 
that  contrast  between  the  cerebral  mass  and  the  spinal  cord, 
which,  in  the  main,  answers  to  the  division  of  nervous 
actions  into  directive  and  executive;  and,  at  the  same  time, 
the  appearance  of  vertebral  laminae  foreshadows  the  separa- 
tion of  the  osseous  system,  which  has  to  resist  the  strains  of 
muscular  action,  from  the  muscular  system,  which,  in  gene- 
rating motion,  entails  these  strains.  Simultaneously  there 
have  been  going  on  similar  actual  and  potential  specializa- 
tions in  the  functions  of  accumulating  energy  and  transfer- 
ring energy.  And  throughout  all  subsequent  phases  the 
method  is  substantially  the  same. 

This  progress  from  general,  indefinite,  and  simple  kinds 
of  action  to  special,  definite,  and  complex  kinds  of  action, 
has  been  aptly  termed  by  Milne-Edwards,  "  the  physiological 
division  of  labour."  Perhaps  no  metaphor  can  more  truly 
express  the  nature  of  this  advance  from  vital  activity  in  its 
lowest  forms  to  vital  activity  in  its  highest  forms.  And 
probably  the  general  reader  cannot  in  any  other  way  obtain 
so  clear  a  conception  of  functional  development  in  organisms, 
as  he  can  by  tracing  out  functional  development  in  societies : 
noting  how  there  first  comes  a  distinction  between  the  govern- 
ing class  and  the  governed  class;  how  while  in  the  govern- 
ing class  there  slowly  grow  up  such  differences  of  duty  as  the 
civil,  military,  and  ecclesiastical,  there  arise  in  the  governed 
class  fundamental  industrial  differences  like  those  between 
agriculturists  and  artizans;  and  how  there  is  a  continual 
multiplication  of  such  specialized  occupations  and  special- 
ized shares  of  each  occupation. 

§  59.  Fully  to  understand  this  change  from  homogeneity 
of  function  to  heterogeneity  of  function,  which  accompanies 
the  change  from  homogeneity  of  structure  to  heterogeneity  of 
structure,  it  is  needful  to  contemplate  it  under  a  converse 


FUNCTION.  205 

aspect.  Standing  alone,  the  above  exposition  conveys  an 
idea  that  is  both  inadequate  and  erroneous.  The  divisions 
and  subdivisions  of  function,  becoming  definite  as  they  be- 
come multiplied,  do  not  lead  to  a  more  and  more  complete 
independence  of  functions;  as  they  would  do  were  the  pro- 
cess nothing  beyond  that  just  described;  but  by  a  simul- 
taneous process  they  are  rendered  more  mutually  dependent. 
While  in  one  respect  they  are  separating  from  each  other, 
they  are  in  another  respect  combining  with  each  other.  At 
the  same  time  that  they  are  being  differentiated  they  are  also 
being  integrated.  Some  illustrations  will  make  this  plain. 

In  animals  which  display  little  beyond  the  primary  dif- 
ferentiation of  functions,  the  activity  of  that  part  which 
absorbs  nutriment  or  accumulates  energy,  is  not  immediately 
bound  up  with  the  activity  of  that  part  which,  in  producing 
motion,  expends  energy.  In  the  higher  animals,  however,  the 
performance  of  the  alimentary  functions  depends  on  the  per- 
formance of  various  muscular  and  nervous  functions.  Masti- 
cation and  swallowing  are  nervo-muscular  acts;  the  rhyth- 
mical contractions  of  the  stomach  and  the  allied  vermicular 
motions  of  the  intestines,  result  from  the  reflex  stimulation 
of  certain  muscular  coats  caused  by  food;  the  secretion  of 
the  several  digestive  fluids  by  their  respective  glands,  is  due 
to  nervous  excitation  of  them ;  and  digestion,  besides  requir- 
ing these  special  aids,  is  not  properly  performed  in  the 
absence  of  a  continuous  discharge  of  energy  from  the  great 
nervous  centres.  Again,  the  function  of  transferring 

nutriment  or  latent  energy,  from  part  to  part,  though  at  first 
not  closely  connected  with  the  other  functions,  eventually 
becomes  so.  The  short  contractile  tube  which  propels  back- 
wards and  forwards  the  blood  contained  in  the  peri-visceral 
cavity  of  an  ascidian,  is  neither  structurally  nor  functionally 
much  entangled  with  the  creature's  other  organs.  But  on 
passing  upwards  through  higher  types,  in  which  this  simple 
tube  is  replaced  by  a  system  of  branched  tubes,  that  deliver 
their  contents  through  their  open  ends  into  the  tissues  at 


206  THE  INDUCTIONS  OF  BIOLOGY. 

distant  parts;  and  on  coming  to  those  advanced  types  which 
have  closed  arterial  and  venous  systems,  ramifying  minutely 
in  every  corner  of  every  organ;  we  find  that  the  vascular 
apparatus,  while  it  has  become  structurally  interwoven  with 
the  whole  body,  has  become  unable  properly  to  fulfil  its  office 
without  the  help  of  offices  that  are  quite  separated  from  its 
own.  The  heart,  though  mainly  automatic  in  its  actions,  is 
controlled  by  the  nervous  system,  which  takes  a  share  in 
regulating  the  contractions  both  of  the  heart  and  the 
arteries.  On  the  due  discharge  of  the  respiratory  function, 
too,  the  function  of  circulation  is  directly  dependent :  if  the 
aeration  of  the  blood  is  impeded  the  vascular  activity  is 
lowered;  and  arrest  of  the  one  very  soon  causes  stoppage  of 
the  other.  Similarly  with  the  duties  of  the  nervo- 

muscular  system.  Animals  of  low  organization,  in  which 
the  differentiation  and  integration  of  the  vital  actions  have 
not  been  carried  far,  will  move  about  for  a  considerable  time 
after  being  eviscerated,  or  deprived  of  those  appliances  by 
which  energy  is  accumulated  and  transferred.  But  animals 
of  high  organization  are  instantly  killed  by  the  removal  of 
these  appliances,  and  even  by  the  injury  of  minor  parts  of 
them:  a  dog's  movements  are  suddenly  brought  to  an  end, 
by  cutting  one  of  the  main  canals  along  which  the  materials 
that  evolve  movements  are  conveyed.  Thus  while 

in  well-developed  creatures  the  distinction  of  functions  is 
very  marked,  the  combination  of  functions  is  very  close. 
From  instant  to  instant  the  aeration  of  blood  implies  that 
certain  respiratory  muscles  are  being  made  to  contract  by 
nervous  impulses  passing  along  certain  nerves;  and  that  the 
heart  is  duly  propelling  the  blood  to  be  aerated.  From 
instant  to  instant  digestion  proceeds  only  on  condition  that 
there  is  a  supply  of  aerated  blood,  and  a  due  current  of 
nervous  energy  through  the  digestive  organs.  That  the  heart 
of  a  mammal  may  act,  its  muscle  substance  must  be  con- 
tinuously fed  with  an  abundant  supply  of  arterial  blood.. 
It  is  not  easy  to  find  an  adequate  expression  for  this  double 


FUNCTION.  207 

re-distribution  of  functions.  It  is  not  easy  to  realize  a  trans- 
formation through  which  the  functions  thus  become  in  one 
sense  separated  and  in  another  sense  combined,  or  even  inter- 
fused. Here,  however,  as  before,  an  analogy  drawn  from 
social  organization  helps  us.  If  we  observe  how  the  increas- 
ing division  of  labour  in  societies  is  accompanied  by  a  closer 
co-operation ;  and  how  the  agencies  of  different  social  actions, 
while  becoming  in  one  respect  more  distinct,  become  in  another 
respect  more  minutely  ramified  through  one  another;  we 
shall  understand  better  the  increasing  physiological  co- 
operation that  accompanies  increasing  physiological  division 
of  labour.  Note,  for  example,  that  while  local  divi- 

sions and  classes  of  the  community  have  been  growing 
unlike  in  their  several  occupations,  the  carrying  on  of 
their  several  occupations  has  been  growing  dependent  on 
the  due  activity  of  that  vast  organization  by  which  sus- 
tenance is  collected  and  diffused.  During  the  early  stages 
of  social  development,  every  small  group  of  people,  and  often 
every  family,  obtained  separately  its  own  necessaries;  but 
now,  for  each  necessary,  and  for  each  superfluity,  there 
exists  a  combined  body  of  wholesale  and  retail  distributors, 
which  brings  its  branched  channels  of  supply  within  reach  of 
all.  While  each  citizen  is  pursuing  a  business  that  does  not 
immediately  aim  at  the  satisfaction  of  his  personal  wants,  his 
personal  wants  are  satisfied  by  a  general  agency  which  brings 
from  all  places  commodities  for  him  and  his  fellow-citizens 
— an  agency  which  could  not  cease  its  special  duties  for  a  few 
days,  without  bringing  to  an  end  his  own  special  duties  and 
those  of  most  others.  Consider,  again,  how  each 

of  these  differentiated  functions  is  everywhere  pervaded  by 
certain  other  differentiated  functions.  Merchants,  manu- 
facturers, wholesale  distributors  of  their  several  species, 
together  with  lawyers,  bankers,  &c.,  all  employ  clerks.  In 
clerks  we  have  a  specialized  class  dispersed  through  various 
other  classes;  and  having  its  function  fused  with  the  dif- 
ferent functions  of  these  various  other  classes.  Similarly 


208  THE  INDUCTIONS  OF  BIOLOGY. 

commercial  travellers,  though  having  in  one  sense  a 
separate  occupation,  have  in  another  sense  an  occupation 
forming  part  of  each  of  the  many  occupations  which  it 
aids.  As  it  is  here  with  the  sociological  division  of 

labour,  so  is  it  with  the  physiological  division  of  labour 
above  described.  Just  as  we  see  in  an  advanced  community, 
that  while  the  magisterial,  the  clerical,  the  medical,  the  legal, 
the  manufacturing,  and  the  commercial  activities,  have  grown 
distinct,  they  have  yet  their  agencies  mingled  together  in 
every  locality;  so  in  a  developed  organism,  we  see  that  while 
the  general  functions  of  circulation,  secretion,  absorption, 
excretion,  contraction,  excitation,  &c.,  have  become  differ- 
entiated, yet  through  the  ramifications  of  the  systems  appor- 
tioned to  them,  they  are  closely  combined  with  one  another 
in  every  organ. 

§  60.  The  physiological  division  of  labour  is  usually  not 
carried  so  far  as  wholly  to  destroy  the  primary  physiological 
community  of  labour.  As  in  societies  the  adaptation  of  special 
classes  to  special  duties,  does  not  entirely  disable  these  classes 
from  performing  one  another's  duties  on  an  emergency ;  so  in 
organisms,  tissues  and  structures  that  have  become  fitted  to 
the  particular  offices  they  have  ordinarily  to  discharge,  often 
remain  partially  able  to  discharge  other  offices.  It  has  been 
pointed  out  by  Dr.  Carpenter,  that  "  in  cases  where  the  dif- 
ferent functions  are  highly  specialized,  the  general  structure 
retains,  more  or  less,  the  primitive  community  of  function 
which  originally  characterized  it."  A  few  instances  will 
bring  home  this  generalization. 

The  roots  and  leaves  of  plants  are  widely  differentiated  in 
their  functions :  by  the  roots,  water  and  mineral  substances 
are  absorbed;  while  the  leaves  take  in,  and  decompose,  car- 
bonic acid.  Nevertheless,  by  many  botanists  it  is  held  that 
some  leaves,  or  parts  of  them,  can  absorb  water;  and  in  what 
are  popularly  called  "  air-plants,"  or  at  any  rate  in  some 
kinds  of  them,  the  absorption  of  water  is  mainly  and  in 


FUNCTION.  209 

some  cases  wholly  carried  on  by  them  and  by  the  stems. 
Conversely,  the  underground  parts  can  partially  assume  the 
functions  of  leaves.  The  exposed  tuber  of  a  potato  develops 
chlorophyll  on  its  surface,  and  in  other  cases,  as  in  that  of  the 
turnip,  roots,  properly  so  called,  do  the  like.  In  trees  the 
trunks,  which  have  in  great  measure  ceased  to  produce  buds, 
recommence  producing  them  if  the  branches  are  cut  off; 
sometimes  aerial  branches  send  down  roots  to  the  earth;  and 
under  some  circumstances  the  roots,  though  not  in  the 
habit  of  developing  leaf-bearing  organs,  send  up  numerous 
suckers.  When  the  excretion  of  bile  is  arrested,  part 

goes  to  the  skin  and  some  to  the  kidneys,  which  presently 
suffer  under  their  new  task.  Various  examples  of  vicarious 
functions  may  be  found  among  animals.  The  excretion  of 
carbonic  acid  and  absorption  of  oxygen  are  mainly  performed 
by  the  lungs,  in  creatures  which  have  lungs;  but  in  such 
creatures  there  continues  a  certain  amount  of  cutaneous 
respiration,  and  in  soft-skinned  batraehians  like  the  frog, 
this  cutaneous  respiration  is  important.  Again,  when  the 
kidneys  are  not  discharging  their  duties  a  notable  quantity 
of  urea  is  got  rid  of  by  perspiration.  Other  instances 

are  supplied  by  the  higher  functions.  In  man  the  limbs, 
which  among  lower  vertebrates  are  almost  wholly  organs  of 
locomotion,  are  specialized  into  organs  of  locomotion  and 
organs  of  manipulation.  Nevertheless,  the  human  arms  and 
legs  do,  when  needful,  fulfil,  to  some  extent,  each  other's 
offices.  Not  only  in  childhood  and  old  age  are  the  arms 
used  for  purposes  of  support,  but  on  occasions  of  emergency, 
as  when  mountaineering,  they  are  used  by  men  in  full 
vigour.  And  that  legs  are  to  a  considerable  degree  capable 
of  performing  the  duties  of  arms,  is  proved  by  the  great 
amount  of  manipulatory  skill  reached  by  them  when  the 
arms  are  absent.  Among  the  perceptions,  too,  there  are  ex- 
amples of  partial  substitution.  The  deaf  Dr.  Kitto  described 
himself  as  having  become  excessively  sensitive  to  vibrations 
propagated  through  the  body;  and  as  so  having  gained  the 


210  THE  INDUCTIONS  OP  BIOLOGY. 

power  of  perceiving,  through  his  general  sensations,  those 
neighbouring  concussions  of  which  the  ears  ordinarily  give 
notice.  Blind  people  make  hearing  perform,  in  part,  the 
office  of  vision.  Instead  of  identifying  the  positions  and 
sizes  of  neighbouring  objects  by  the  reflection  of  light  from 
their  surfaces,  they  do  this  in  a  rude  way  by  the  reflection  of 
sound  from  their  surfaces. 

We  see,  as  we  might  expect  to  see,  that  this  power  of  per- 
forming more  general  functions,  is  great  in  proportion  as 
the  organs  have  been  but  little  adapted  to  their  special  func- 
tions. Those  parts  of  plants  which  show  so  considerable  an 
ability  to  discharge  each  others'  offices,  are  not  widely  unlike 
in  their  minute  structures.  And  the  tissues  which  in  ani- 
mals are  to  some  extent  mutually  vicarious,  are  tissues  in 
which  the  original  cellular  composition  is  still  conspicuous. 
But  we  do  not  find  evidence  that  the  muscular,  nervous,  or 
osseous  tissues  are  able  in  any  degree  to  perform  those  pro- 
cesses which  the  less  differentiated  tissues  perform.  Nor 
have  we  any  proof  that  nerve  can  partially  fulfil  the  duty  of 
muscle,  or  muscle  that  of  nerve.  We  must  say,  therefore,  that 
the  ability  to  resume  the  primordial  community  of  function, 
varies  inversely  as  the  established  specialization  of  function; 
and  that  it  disappears  when  the  specialization  of  function 
becomes  great. 

§  61.  Something  approaching  to  a  priori  reasons  may  be 
given  for  the  conclusions  thus  reached  a  posteriori.  They 
must  be  accepted  for  as  much  as  they  seem  worth. 

It  may  be  argued  that  on  the  hypothesis  of  Evolution, 
Life  necessarily  comes  before  organization.  On  this  hypo- 
thesis, organic  matter  in  a  state  of  homogeneous  aggregation 
must  precede  organic  matter  in  a  state  of  heterogeneous 
aggregation.  But  since  the  passing  from  a  structureless 
state  to  a  structured  state,  is  itself  a  vital  process,  it  follows 
that  vital  activity  must  have  existed  while  there  was  yet 
no  structure:  structure  could  not  else  arise.  That 


FUNCTION.  211 

function  takes  precedence  of  structure,  seems  also  implied  in 
the  definition  of  Life.  If  Life  is  shown  by  inner  actions  so 
adjusted  as  to  balance  outer  actions — if  the  implied  energy  is 
the  substance  of  Life  while  the  adjustment  of  the  actions 
constitutes  its  form;  then  may  we  not  say  that  the  actions 
to  be  formed  must  come  before  that  which  forms  them — 
that  the  continuous  change  which  is  the  basis  of  function, 
must  come  before  the  structure  which  brings  function  into 
shape  ?  Or  again,  since  in  all  phases  of  Life  up  to  the 

highest,  every  advance  is  the  effecting  of  some  better  adjust- 
ment of  inner  to  outer  actions;  and  since  the  accompanying 
new  complexity  of  structure  is  simply  a  means  of  making 
possible  this  better  adjustment;  it  follows  that  the  achieve- 
ment of  function  is,  throughout,  that  for  which  structure 
arises.  Not  only  is  this  manifestly  true  where  the  modifi- 
cation of  structure  results  by  reaction  from  modification  of 
function ;  but  it  is  also  true  where  a  modification  of  structure 
otherwise  produced,  apparently  initiates  a  modification  of 
function.  For  it  is  only  when  such  so-called  spontaneous 
modification  of  structure  subserves  some  advantageous  action, 
that  it  is  permanently  established.  If  it  is  a  structural 
modification  that  happens  to  facilitate  the  vital  activities, 
"  natural  selection  "  retains  and  increases  it ;  but  if  not,  it 
disappears. 

The  connexion  which  we  noted  between  heterogeneity  of 
structure  and  heterogeneity  of  function — a  connexion  made 
so  familiar  by  experience  as  to  appear  scarcely  worth  specify- 
ing— is  clearly  a  necessary  one.  It  follows  from  the  general 
truth  that  in  proportion  to  the  heterogeneity  of  any  aggregate, 
is  the  heterogeneity  it  will  produce  in  any  incident  force 
(First  Principles,  §  156).  The  energy  continually  liberated 
in  the  organism  by  decomposition,  is  here  the  incident  force; 
the  functions  are  the  variously  modified  forms  produced  in 
its  divisions  by  the  organs  they  pass  through;  and  the  more 
multiform  the  organs  the  more  multiform  must  be  the  dif- 
ferentiations of  the  force  passing  through  them. 


212  THE  INDUCTIONS  OP  BIOLOGY. 

It  follows  obviously  from  this,  that  if  structure  progresses 
from  the  homogeneous,  indefinite,  and  incoherent,  to  the 
heterogeneous,  definite,  and  coherent,  so  too  must  function. 
If  the  number  of  different  parts  in  an  aggregate  must  deter- 
mine the  number  of  differentiations  produced  in  the  energies 
passing  through  it— if  the  distinctness  of  these  parts  from 
one  another,  must  involve  distinctness  in  their  reactions,  and 
therefore  distinctness  between  the  divisions  of  the  differen- 
tiated energy;  there  cannot  but  be  a  complete  parallelism 
between  the  development  of  structure  and  the  development 
of  function.  If  structure  advances  from  the  simple  and  gene- 
ral to  the  complex  and  special,  function  must  do  the  same. 


CHAPTER  IV. 

WASTE     AND     REPAIR. 

§  62.  THROUGHOUT  the  vegetal  kingdom,  the  processes  of 
Waste  and  Eepair  are  comparatively  insignificant  in  their 
amounts.  Though  all  parts  of  plants  save  the  leaves,  or 
other  parts  which  are  green,  give  out  carbonic  acid ;  yet  this 
carbonic  acid,  assuming  it  to  indicate  consumption  of  tissue, 
or  rather  of  the  protoplasm  contained  in  the  tissue,  indicates 
but  a  small  consumption.  Of  course  if  there  is  little  waste 
there  can  be  but  little  repair — that  is,  little  of  the  interstitial 
repair  which  restores  the  integrity  of  parts  worn  by  func- 
tional activity.  Nor,  indeed,  is  there  displayed  by  plants  in 
any  considerable  degree,  if  at  all,  that  other  species  of  repair 
which  consists  in  the  restoration  of  lost  or  injured  organs. 
Torn  leaves  and  the  shoots  that  are  shortened  by  the  pruner, 
do  not  reproduce  their  missing  parts;  and  though  when  the 
branch  of  a  tree  is  cut  off  close  to  the  trunk,  the  place  is  in 
course  of  years  covered  over,  it  is  not  by  any  reparative 
action  in  the  wounded  surface  but  by  the  lateral  growth  of 
the  adjacent  bark.  Hence,  without  saying  that  Waste  and 
Repair  do  not  go  on  at  all  in  plants,  we  may  fitly  pass  them 
over  as  of  no  importance. 

There  are  but  slight  indications  of  waste  in  those  lower 

orders  of  animals  which,  by  their  comparative   inactivity, 

show  themselves  least  removed  from  vegetal  life.      Actinia? 

kept  in  an  aquarium,  do  not  appreciably  diminish  in  bulk 

15  213 


214  THE  INDUCTIONS  OP  BIOLOGY. 

from  prolonged  abstinence.  Even  fish,  though  much  more 
active  than  most  other  aquatic  creatures,  appear  to  undergo 
hut  little  loss  of  substance  when  kept  unfed  during  consider- 
able periods.  Reptiles,  too,  maintaining  no  great  tempera- 
ture, and  passing  their  lives  mostly  in  a  state  of  torpor,  suffer 
but  little  diminution  of  mass  by  waste.  When,  however,  we 
turn  to  those  higher  orders  of  animals  which  are  active  and 
hot-blooded,  we  see  that  waste  is  rapid:  producing,  when 
unchecked,  a  notable  decrease  in  bulk  and  weight,  ending 
very  shortly  in  death.  Besides  finding  that  waste  is 

inconsiderable  in  creatures  which  produce  but  little  insensible 
and  sensible  motion,  and  that  it  becomes  conspicuous  in 
creatures  which  produce  much  insensible  and  sensible  motion ; 
we  find  that  in  the  same  creatures  there  is  most  waste  when 
most  motion  is  generated.  This  is  clearly  proved  by  hyber- 
nating  animals.  "  Valentin  found  that  the  waking  marmot 
excreted  in  the  average  75  times  more  carbonic  acid,  and 
inhaled  41  times  more  oxygen  than  the  same  animal  in  the 
most  complete  state  of  hybernation.  The  stages  between 
waking  and  most  profound  hybernation  yielded  intermediate 
figures.  A  waking  hedgehog  yielded  about  20.5  times  more 
carbonic  acid,  and  consumed  18.4  times  more  oxygen  than 
one  in  the  state  of  hybernation."  *  If  we  take  these  quanti- 
ties of  absorbed  oxygen  and  excreted  carbonic  acid,  as  in- 
dicating something  like  the  relative  amounts  of  consumed 
organic  substance,  we  see  that  there  is  a  striking  contrast 
between  the  waste  accompanying  the  ordinary  state  of 
activity,  and  the  waste  accompanying  complete  quiescence 
and  reduced  temperature.  This  difference  is  still  more  defi- 
nitely shown  by  the  fact,  that  the  mean  daily  loss  from 
starvation  in  rabbits  and  guinea-pigs,  bears  to  that  from 

*  In  connexion  with  this  matter  I  add  here  a  statement  made  by  Prof. 
Foster  which  it  is  difficult  to  understand:  "Indeed  it  has  been  observed 
that  a  dormouse  actually  gained  in  weight  during  a  hybernating  period ;  it 
discharged  during  this  period  neither  urine  nor  faeces,  and  the  gain  in 
weight  was  the  excess  of  oxygen  taken  in  over  the  carbonic  acid  given  out." 
(Text-book  of  Phytiology,  6th  ed.,  Part  II,  page  869.) 


WASTE  AND  REPAIR.  215 

hybernation,  the  proportion  of  18.3  :  1.  Among  men  and 
domestic  animals,  the  relation  between  degree  of  waste  and 
amount  of  expended  energy,  though  one  respecting  which 
there  is  little  doubt,  is  less  distinctly  demonstrable;  since 
waste  is  not  allowed  to  go  on  uninterfered  with.  We  have, 
however,  in  the  lingering  lives  of  invalids  who  are  able  to  take 
scarcely  any  nutriment  but  are  kept  warm  and  still,  an  illus- 
tration of  the  extent  to  which  waste  diminishes  as  the  ex- 
penditure of  energy  declines. 

Besides  the  connexion  between  the  waste  of  the  organism 
as  a  whole  and  the  production  of  sensible  and  insensible 
motion  by  the  organism  as  a  whole,  there  is  a  traceable  con- 
nexion between  the  waste  of  special  parts  and  the  activities 
of  such  special  parts.  Experiments  have  shown  that  "  the 
starving  pigeon  daily  consumes  in  the  average  40  times  more 
muscular  substance  that  the  marmot  in  the  state  of  torpor, 
and  only  11  times  more  fat,  33  times  more  of  the  tissue 
of  the  alimentary  canal,  18.3  times  more  liver,  15  times 
more  lung,  5  times  more  skin."  That  is  to  say,  in  the 
hybernating  animal  the  parts  least  consumed  are  the  almost 
totally  quiescent  motor-organs,  and  the  part  most  consumed 
is  the  hydro-carbonaceous  deposit  serving  as  a  store  of  energy ; 
whereas  in  the  pigeon,  similarly  unsupplied  with  food  but 
awake  and  active,  the  greatest  loss  takes  place  in  the  motor- 
organs.  The  relation  between  special  activity  and 
special  waste,  is  illustrated,  too,  in  the  daily  experiences  of 
all :  not  indeed  in  the  amount  of  decrease  of  the  active  parts 
in  bulk  or  weight,  for  this  we  have  no  means  of  ascertaining ; 
but  in  the  diminished  ability  of  such  parts  to  perform  their 
functions.  That  legs  exerted  for  many  hours  in  walking  and 
arms  long  strained  in  rowing,  lose  their  powers — that  eyes 
become  enfeebled  by  reading  or  writing  without  intermission 
— that  concentrated  attention,  unbroken  by  rest,  so  prostrates 
the  brain  as  to  incapacitate  it  for  thinking;  are  familiar 
truths.  And  though  we  have  no  direct  evidence  to  this  effect, 
there  is  little  danger  in  concluding  that  muscles  exercised 


216  THE  INDUCTIONS  OF   BIOLOGY. 

until  they  ache  or  become  stiff,  and  nerves  of  sense  rendered 
weary  or  obtuse  by  work,  are  organs  so  much  wasted  by  action 
as  to  be  partially  incompetent. 

Repair  is  everywhere  and  always  making  up  for  waste. 
Though  the  two  processes  vary  in  their  relative  rates  both 
are  constantly  going  on.  Though  during  the  active,  waking 
state  of  an  animal  waste  is  in  excess  of  repair,  yet  repair  is 
in  progress;  and  though  during  sleep  repair  is  in  excess  of 
waste,  yet  some  waste  is  necessitated  by  the  carrying  on  of 
certain  -never-ceasing  functions.  The  organs  of  these  never- 
ceasing  functions  furnish,  indeed,  the  most  conclusive  proofs 
of  the  simultaneity  of  repair  and  waste.  Day  and  night  the 
heart  never  stops  beating,  but  only  varies  in  the  rapidity  and 
vigour  of  its  beats ;  and  hence  the  loss  of  substance  which  its 
contractions  from  moment  to  moment  entail,  must  from 
moment  to  moment  be  made  good.  Day  and  night  the  lungs 
dilate  and  collapse;  and  the  muscles  which  make  them  do 
this  must  therefore  be  kept  in  a  state  of  integrity  by  a  repair 
which  keeps  pace  with  waste,  or  which  alternately  falls  behind 
and  gets  in  advance  of  it  to  a  very  slight  extent. 

On  a  survey  of  the  facts  we  see,  as  we  might  expect  to  see, 
that  the  progress  of  repair  is  most  rapid  when  activity  is 
most  reduced.  Assuming  that  the  organs  which  absorb  and 
circulate  nutriment  are  in  proper  order,  the  restoration  of 
the  body  to  a  state  of  integrity,  after  the  disintegration  con- 
sequent on  expenditure  of  energy,  is  proportionate  to  the 
diminution  in  expenditure  of  energy.  Thus  we  all  know  that 
those  who  are  in  health,  feel  the  greatest  return  of  vigour 
after  profound  sleep — after  complete  cessation  of  motion. 
We  know  that  a  night  during  which  the  quiescence,  bodily 
and  mental,  has  been  less  decided,  is  usually  not  followed  by 
that  spontaneous  overflow  of  energy  which  indicates  a  high 
state  of  efficiency  throughout  the  organism.  We  know, 
again,  that  long-continued  recumbency,  even  with  wakeful- 
ness  (providing  the  wakefulness  is  not  the  result  of  disorder), 
is  followed  by  a  certain  renewal  of  strength;  though  a  re- 


WASTE  AND  REPAIR.  217 

newal  less  than  that  which  would  have  followed  the  greater 
inactivity  of  slumber.  We  know,  too,  that  when  exhausted 
by  labour,  sitting  brings  a  partial  return  of  vigour.  And 
we  also  know  that  after  the  violent  exertion  of  running, 
a  lapse  into  the  less  violent  exertion  of  walking,  results  in  a 
gradual  disappearance  of  that  prostration  which  the  running 
produced.  This  series  of  illustrations  conclusively  proves 
that  the  rebuilding  of  the  organism  is  ever  making  up  for 
the  pulling  down  of  it  caused  by  action;  and  that  the  effect 
of  this  rebuilding  becomes  more  manifest,  in  proportion  as 
the  pulling  down  is  less  rapid.  From  each  digested  meal 
there  is  every  few  hours  absorbed  into  the  mass  of  prepared 
nutriment  circulating  through  the  body,  a  fresh  supply  of 
the  needful  organic  compounds;  and  from  the  blood,  thus 
occasionally  re-enriched,  the  organs  through  which  it  passes 
are  ever  taking  up  materials  to  replace  the  materials  used  up 
in  the  discharge  of  functions.  During  activity  the  reinte- 
gration  falls  in  arrear  of  the  disintegration ;  until,  as  a  conse- 
quence, there  presently  comes  a  general  state  of  functional 
languor;  ending,  at  length,  in  a  quiescence  which  permits 
the  reintegration  to  exceed  the  disintegration,  and  restore  the 
parts  to  their  state  of  integrity.  Here,  as  wherever  there 
are  antagonistic  actions,  we  see  rhythmical  divergences  on 
opposite  sides  of  the  medium  state — changes  which  equilibrate 
each  other  by  their  alternate  excesses.  (First  Principles, 
§§85,  173.) 

Illustrations  are  not  wanting  of  special  repair  that  is 
similarly  ever  in  progress,  and  similarly  has  intervals  during 
which  it  falls  below  waste  and  rises  above  it.  Every  one 
knows  that  a  muscle,  or  a  set  of  muscles,  continuously  strained, 
as  by  holding  out  a  weight  at  arm's  length,  soon  loses  its 
power ;  and  that  it  recovers  its  power  more  or  less  fully  after 
a  short  rest.  The  several  organs  of  the  special  sensations 
yield  us  like  experiences.  Strong  tastes,  powerful  odours,  loud 
sounds,  temporarily  unfit  the  nerves  impressed  by  them  for 
appreciating  faint  tastes,  odours,  or  sounds;  but  these  inca- 


218  THE  INDUCTIONS  OF  BIOLOGY. 

pacities  are  remedied  by  brief  intervals  of  repose.  Vision 
still  better  illustrates  this  simultaneity  of  waste  and  repair. 
Looking  at  the  Sun  so  affects  the  eyes  that,  for  a  short  time, 
they  cannot  perceive  the  things  around  with  the  usual  clear- 
ness. After  gazing  at  a  bright  light  of  a  particular  colour,  we 
see,  on  turning  the  eyes  to  adjacent  objects,  an  image  of  the 
complementary  colour;  showing  that  the  retina  has,  for  the 
moment,  lost  the  power  to  feel  small  amounts  of  those  rays 
which  have  strongly  affected  it.  Such  inabilities  disappear 
in  a  few  seconds  or  a  few  minutes,  according  to  circumstances. 
And  here,  indeed,  we  are  introduced  to  a  conclusive  proof 
that  special  repair  is  ever  neutralizing  special  waste.  For 
the  rapidity  with  which  the  eyes  recover  their  sensitiveness, 
varies  with  the  reparative  power  of  the  individual.  In  youth 
the  visual  apparatus  is  so  quickly  restored  to  its  state  of  in- 
tegrity, that  many  of  these  photogenes,  as  they  are  called, 
cannot  be  perceived.  When  sitting  on  the  far  side  of  a  room, 
and  gazing  out  of  the  window  against  a  light  sky,  a  person 
who  is  debilitated  by  disease  or  advancing  years,  perceives, 
on  transferring  the  gaze  to  the  adjacent  wall,  a  momentary 
negative  image  of  the  window — the  sash-bars  appearing  light 
and  the  squares  dark;  but  a  young  and  healthy  person  has 
no  such  experience.  With  a  rich  blood  and  vigorous  circu- 
lation, the  repair  of  the  visual  nerves  after  impressions  of 
moderate  intensity,  is  nearly  instantaneous. 

Function  carried  to  excess  may  produce  waste  so  great 
that  repair  cannot  make  up  for  it  during  the  ordinary  daily 
periods  of  rest;  and  there  may  result  incapacities  of  the 
over-taxed  organs,  lasting  for  considerable  periods.  We 
know  that  eyes  strained  by  long-continued  minute  work  lose 
their  power  for  months  or  years :  perhaps  suffering  an  injury 
from  which  they  never  wholly  recover.  Brains,  too,  are  often 
so  unduly  worked  that  permanent  relaxation  fails  to  restore 
them  to  vigour.  Even  of  the  motor  organs  the  like  holds. 
The  most  frequent  cause  of  what  is  called  "  wasting  palsy," 
or  atrophy  of  the  muscles,  is  habitual  excess  of  exertion :  the 


WASTE  AND  REPAIR.  219 

proof  being  that  the  disease  occurs  most  frequently  among 
those  engaged  in  laborious  handicrafts,  and  usually  attacks 
first  the  muscles  which  have  been  most  worked. 

There  has  yet  to  be  noticed  another  kind  of  repair — that, 
namely,  by  which  injured  or  lost  parts  are  restored.  Among 
the  Hydrozoa  it  is  common  for  any  portion  of  the  body  to  re- 
produce the  rest;  even  though  the  rest  to  be  so  reproduced 
is  the  greater  part  of  the  whole.  In  the  more  highly-organ- 
ized Actinozoa  the  half  of  an  individual  will  grow  into  a 
complete  individual.  Some  of  the  lower  Annelids,  as  the 
Nais,  may  be  cut  into  thirty  or  forty  pieces  and  each  piece  will 
eventually  become  a  perfect  animal.  As  we  ascend  to  higher 
forms  we  find  this  reparative  power  much  diminished,  though 
still  considerable.  The  reproduction  of  a  lost  claw  by  a 
lobster  or  crab,  is  a  familiar  instance.  Some  of  the  inferior 
Vertebrata  also,  as  lizards,  can  develop  new  limbs  or  new  tails, 
in  place  of  those  which  have  been  cut  off;  and  can  even  do 
this  several  times  over,  though  with  decreasing  complete- 
ness. The  highest  animals,  however,  thus  repair  themselves 
to  but  a  very  small  extent.  Mammals  and  birds  do  it  only 
in  the  healing  of  wounds;  and  very  often  but  imperfectly 
even  in  this.  For  in  muscular  and  glandular  organs  the 
tissues  destroyed  are  not  properly  reproduced,  but  are  re- 
placed by  tissue  of  an  irregular  kind  which  serves  to  hold 
the  parts  together.  So  that  the  power  of  reproducing  lost 
parts  is  greatest  where  the  organization  is  lowest ;  and  almost 
disappears  where  the  organization  is  highest.  And  though 
we  cannot  say  that  in  the  intermediate  stages  there  is  a  con- 
stant inverse  relation  between  reparative  power  and  degree 
of  organization ;  yet  we  may  say  that  there  is  some  approach 
to  such  a  relation. 

§  63.  There  is  an  obvious  and  complete  harmony  between 
the  first  of  the  above  inductions  and  the  deduction  which 
follows  immediately  from  first  principles.  We  have  already 
seen  (§23)  "that  whatever  amount  of  power  an  organism 


220  THE  INDUCTIONS  OP  BIOLOGY. 

expends  in  any  shape,  is  the  correlate  and  equivalent  of  a 
power  that  was  taken  into  it  from  without."  Motion, 
sensible  or  insensible,  generated  by  an  organism,  is  insensible 
motion  which  was  absorbed  in  producing  certain  chemical 
compounds  appropriated  by  the  organism  under  the  form  of 
food.  As  much  energy  as  was  required  to  raise  the  elements 
of  these  complex  atoms  to  their  state  of  unstable  equilibrium, 
is  given  out  in  their  falls  to  a  state  of  stable  equilibrium; 
and  having  fallen  to  a  state  of  stable  equilibrium  they  can 
give  out  no  further  energy,  but  have  to  be  got  rid  of  as  inert 
and  useless.  It  is  an  inevitable  corollary  "  from  the  per- 
sistence of  force,  that  each  portion  of  mechanical  or  other 
energy  which  an  organism  exerts,  implies  the  transforma- 
tion of  as  much  organic  matter  as  contained  this  energy  in 
a  latent  state ; "  and  that  this  organic  matter  in  yielding 
up  its  latent  energy,  loses  its  value  for  the  purposes  of  life, 
and  becomes  waste  matter  needing  to  be  excreted.  The  loss 
of  these  complex  unstable  substances  must  hence  be  pro- 
portionate to  the  quantity  of  expended  force.  Here,  then, 
is  the  rationale  of  certain  general  facts  lately  indicated. 
Plants  do  not  waste  to  any  considerable  degree,  for  the  obvi- 
ous reason  that  the  sensible  and  insensible  motions  they 
generate  are  inconsiderable.  Between  the  small  waste,  small 
activity,  and  low  temperature  of  the  inferior  animals,  the 
relation  is  similarly  one  admitting  of  a  priori  establishment. 
Conversely,  the  rapid  waste  of  energetic,  hot-blooded  animals 
might  be  foreseen  with  equal  certainty.  And  not  less  mani- 
festly necessary  is  the  variation  in  waste  which,  in  the  same 
organism,  attends  the  variation  in  the  heat  and  mechanical 
motion  produced. 

Between  the  activity  of  a  special  part  and  the  waste  of 
that  part,  a  like  relation  may  be  deductively  inferred ;  though 
it  cannot  be  inferred  that  this  relation  is  equally  definite. 
Were  the  activity  of  every  organ  quite  independent  of  the 
activities  of  other  organs,  we  might  expect  to  trace  out  this 
relation  distinctly;  but  since  increased  activity  in  any  organ 


WASTE  AND  REPAIR.  221 

or  group  of  organs,  as  the  muscles,  necessarily  entails  in- 
creased activity  in  other  organs,  as  in  the  heart,  lungs,  and 
nervous  system,  it  is  clear  that  special  waste  and  general 
waste  are  too  much  entangled  to  admit  of  a  definite  relation 
being  established  between  special  waste  and  special  activity. 
We  may  fairly  say,  however,  that  this  relation  is  quite  as 
manifest  as  we  can  reasonably  anticipate. 

§  CA.  Deductive  interpretation  of  the  phenomena  of  Ke- 
pair,  is  by  no  means  so  easy.  The  tendency  displayed  by  an 
animal  organism,  as  well  as  by  each  of  its  organs,  to  return  to 
a  state  of  integrity  by  the  assimilation  of  new  matter,  when  it 
has  undergone  the  waste  consequent  on  activity,  is  a  tendency 
which  is  not  manifestly  deducible  from  first  principles; 
though  it  appears  to  be  in  harmony  with  them.  If  in  the 
blood  there  existed  ready-formed  units  exactly  like  in  kind 
to  those  of  which  each  organ  consists,  the  sorting  of  these 
units,  ending  in  the  union  of  each  kind  with  already  existing 
groups  of  the  same  kind,  would  be  merely  a  good  example  of 
Segregation  (First  Principles^  §  163).  It  would  be  analogous 
to  the  process  by  which,  from  a  mixed  solution  of  salts,  there 
are,  after  an  interval,  deposited  separate  masses  of  these 
salts  in  the  shape  of  different  crystals.  But  as  already  said 
(§  54).  though  the  selective  assimilation  by  which  the  re- 
pair of  organs  is  effected,  may  result  in  part  from  an  action 
of  this  kind,  the  facts  cannot  be  thus  wholly  accounted  for; 
since  organs  are  in  part  made  up  of  units  which  do  not  exist 
as  such  in  the  circulating  fluids.  We  must  suppose  that,  as 
suggested  in  §  54,  groups  of  compound  units  have  a  certain 
power  of  moulding  adjacent  fit  materials  into  units  of  their 
own  form.  Let  us  see  whether  there  is  not  reason  to  think 
such  a  power  exists. 

"  The  poison  of  small-pox  or  of  scarlatina,"  remarks  Mr. 
(now  Sir  James)  Paget,  "  being  once  added  to  the  blood,  pres- 
ently affects  the  composition  of  the  whole :  the  disease  pursues 
its  course,  and,  if  recovery  ensue,  the  blood  will  seem  to  have 


222  THE  INDUCTIONS  OP  BIOLOGY. 

returned  to  its  previous  condition:  yet  it  is  not  as  it  was  be- 
fore; for  now  the  same  poison  may  be  added  to  it  with  im- 
punity." ..."  The  change  once  effected,  may  be  maintained 
through  life.  And  herein  seems  to  be  a  proof  of  the  assimil- 
ative force  in  the  blood:  for  there  seems  no  other  mode  of 
explaining  these  cases  than  by  admitting  that  the  altered 
particles  have  the  power  of  assimilating  to  themselves  all 
those  by  which  they  are  being  replaced :  in  other  words,  all 
the  blood  that  is  formed  after  such  a  disease  deviates  from 
the  natural  composition,  so  far  as  to  acquire  the  peculiarity 
engendered  by  the  disease:  it  is  formed  according  to  the 
altered  model."  Now  if  the  compound  molecules  of  the 
blood,  or  of  an  organism  considered  in  the  aggregate,  have 
the  power  of  moulding  into  their  own  type  the  matters  which 
they  absorb  as  nutriment;  and  if  they  have  the  power  when 
their  type  has  been  changed  by  disease,  of  moulding  materials 
afterwards  received  into  the  modified  type;  may  we  not 
reasonably  suspect  that  the  more  or  less  specialized  molecules 
of  each  organ  have,  in  like  manner,  the  power  of  moulding 
the  materials  which  the  blood  brings  to  them  into  similarly 
specialized  molecules?  The  one  conclusion  seems  to  be  a 
corollary  from  the  other.  Such  a  power  cannot  be  claimed 
for  the  component  units  of  the  blood  without  being  con- 
ceded to  the  component  units  of  every  tissue.  Indeed  the 
assertion  of  this  power  is  little  more  than  an  assertion  of  the 
fact  that  organs  composed  of  specialized  units  are  capable 
of  resuming  their  structural  integrity  after  they  have  been 
wasted  by  function.  For  if  they  do  this,  they  must  do  it  by 
forming  from  the  materials  brought  to  them,  certain  special- 
ized units  like  in  kind  to  those  of  which  they  are  composed; 
and  to  say  that  they  do  this,  is  to  say  that  their  component 
units  have  the  power  of  moulding  fit  materials  into  other 
units  of  the  same  order. 

§  65.  What  must  we  say  of  the  ability  an  organism  has 
to  re-complete  itself  when  one  of  its  parts  has  been  gut  off  ? 


WASTE  AND  REPAIR.  223 

Is  it  of  the  same  order  as  the  ability  of  an  injured  crystal  to 
re-complete  itself.  In  either  case  new  matter  is  so  deposited 
as  to  restore  the  original  outline.  And  if  in  the  case  of  the 
crystal  we  say  that  the  whole  aggregate  exerts  over  its  parts  a 
force  which  constrains  the  newly-integrated  molecules  to  take- 
a  certain  definite  form,  we  seem  obliged,  in  the  case  of  the 
organism,  to  assume  an  analogous  force.  If  when  the  leg  of 
a  lizard  has  been  amputated  there  presently  buds  out  the 
germ  of  a  new  one,  which,  passing  through  phases  of  develop- 
ment like  those  of  the  original  leg,  eventually  assumes  a  like 
shape  and  structure,  we  assert  only  what  we  see,  when  we 
assert  that  the  entire  organism,  or  the  adjacent  part  of  it, 
exercises  such  power  over  the  forming  limb  as  makes  it  a 
repetition  of  its  predecessor.  If  a  leg  is  reproduced,  where 
there  was  a  leg,  and  a  tail  where  there  was  a  tail,  there 
seems  no  alternative  but  to  conclude  that  the  forces  around 
it  control  the  formative  processes  going  on  in  each  part. 
And  on  contemplating  these  facts  in  connexion  with  various 
kindred  ones,  there  is  suggested  the  hypothesis,  that  the 
form  of  each  species  of  organism  is  determined  by  a  pecu- 
liarity in  the  constitution  of  its  units — that  these  have  a 
special  structure  in  which  they  tend  to  arrange  themselves; 
just  as  have  the  simpler  units  of  inorganic  matter.  Let  us 
glance  at  the  evidences  which  more  especially  thrust  this 
conclusion  upon  us. 

A  fragment  of  a  Begonia-leaf  imbedded  in  fit  soil  and  kept 
at  an  appropriate  temperature,  Avill  develop  a  young  Begonia ; 
and  so  small  is  the  fragment  which  is  thus  capable  of  origin- 
ating a  complete  plant,  that  something  like  a  hundred 
plants  may  be  produced  from  a  single  leaf.  The  friend  to 
whom  I  owe  this  observation,  tells  me  that  various  succulent 
plants  have  like  powers  of  multiplication.  Illustrating  a 
similar  power  among  animals,  we  have  the  often-cited  experi- 
ments of  Trembley  on  the  common  polype.  Each  of  the 
four  pieces  into  which  one  of  these  creatures  was  cut,  grew 
into  a  perfect  individual.  In  each  of  these,  again,  bisection 


224  THE  INDUCTIONS  OF  BIOLOGY. 

and  tri-section  were  followed  by  like  results.  And  so  with 
their  segments,  similarly  produced,  until  as  many  as  fifty 
polypes  had  resulted  from  the  original  one.  Bodies  when  cut 
off  regenerated  heads;  heads  regenerated  bodies;  and  when 
a  polype  had  been  divided  into  as  many  pieces  as  was  prac- 
ticable, nearly  every  piece  survived  and  became  a  complete 
animal.  What,  now,  is  the  implication?  We  cannot 

say  that  in  each  portion  of  a  Begonia-leaf,  and  in  every 
fragment  of  a  Hydra's  body,  there  exists  a  ready-formed 
model  of  the  entire  organism.  Even  were  there  warrant  for 
the  doctrine  that  the  germ  of  every  organism  contains  the 
perfect  organism  in  miniature,  it  still  could  not  be  contended 
that  each  considerable  part  of  the  perfect  organism  resulting 
from  such  a  germ,  contains  another  such  miniature.  Indeed 
the  one  hypothesis  negatives  the  other.  The  implication 
seems,  therefore,  to  be  that  the  living  particles  composing  one 
of  these  fragments,  have  an  innate  tendency  to  arrange  them- 
selves into  the  shape  of  the  organism  to  which  they  belong. 
We  must  infer  that  the  active  units  composing  a  plant  or 
animal  of  any  species  have  an  intrinsic  aptitude  to  aggregate 
into  the  form  of  that  species.  It  seems  difficult  to  conceive 
that  this  can  be  so;  but  we  see  that  it  is  so.  Groups  of 
units  taken  from  an  organism  (providing  they  are  of  a  certain 
bulk  and  not  much  differentiated  into  special  structures)  have 
this  power  of  re-arranging  themselves.  Manifestly, 

too,  if  we  are  thus  to  interpret  the  reproduction  of  an  organism 
from  one  of  its  amorphous  fragments,  we  must  thus  interpret 
the  reproduction  of  any  minor  portion  of  an  organism  by  the 
remainder.  When  in  place  of  its  lost  claw  a  lobster  puts 
forth  a  cellular  mass  which,  while  increasing  in  bulk,  assumes 
the  form  and  structure  of  the  original  claw,  we  cannot  avoid 
ascribing  this  result  to  a  play  of  forces  like  that  which  moulds 
the  materials  contained  in  a  piece  of  Begonia-leaf  into  the 
shape  of  a  young  Begonia. 

§  66.  As  we  shall  have  frequent  occasion  hereafter  to  refer 


WASTE  AND  REPAIR.  225 

to  these  units  which  possess  the  property  of  arranging  them- 
selves into  the  special  structures  of  the  organisms  to  which 
they  belong;  it  will  be  well  here  to  ask  by  what  name  they 
may  be  most  fitly  called. 

On  the  one  hand,  it  cannot  .be  in  those  chemica.1  com- 
pounds characterizing  organic  bodies  that  this  specific  pro- 
perty dwells.  It  cannot  be  that  the  molecules  of  albumin, 
or  fibrin,  or  gelatine,  or  other  proteid,  possess  this  power  of 
aggregating  into  these  specific  shapes ;  for  in  such  case  there 
would  be  nothing  to  account  for  the  unlikenesses  of  different 
organisms.  If  the  proclivities  of  proteid  molecules  deter- 
mined the  forms  of  the  organisms  built  up  of  them  or  by 
them,  the  occurrence  of  such  endlessly  varied  forms  would 
be  inexplicable.  Hence  what  we  may  call  the  chemical  units 
are  clearly  not  the  possessors  of  this  property. 

On  the  other  hand,  this  property  cannot  reside  in  what 
may  be  roughly  distinguished  as  the  morphological  units.  The 
germ  of  every  organism  is  a  minute  portion  of  encased  pro- 
toplasm commonly  called  a  cell.  It  is  by  multiplication  of 
cells  that  all  the  early  developmental  changes  are  effected. 
The  various  tissues  which  successively  arise  in  the  unfolding 
organism,  are  primarily  cellular;  and  in  many  of  them  the 
formation  of  cells  continues  to  be,  throughout  life,  the  process 
by  which  repair  is  carried  on.  But  though  cells  are  so 
generally  the  'ultimate  visible  components  of  organisms,  that 
they  may  with  some  show  of  reason  be  called  the  morpholo- 
gical units;  yet  we  cannot  say  that  this  tendency  to  aggre- 
gate into  special  forms  dwells  in  them.  In  many  cases  a 
fibrous  tissue  arises  out  of  a  nucleated  blastema,  without 
cell-formation ;  and  in  such  cases  cells  cannot  be  regarded  as 
units  possessing  the  structural  proclivity.  But  the  conclusive 
proof  that  the  morphological  units  are  not  the  building 
factors  in  an  organism  composed  of  them,  is  yielded  by  their 
independent  homologues  the  so-called  unicellular  organisms. 
For  each  of  these  displays  the  power  to  assume  its  specific 
structure.  Clearly,  if  the  ability  of  a  multicellular  organism 


226  THE  INDUCTIONS  OF  BIOLOGY. 

to  assume  its  specific  structure  resulted  from  the  coopera- 
tion of  its  component  cells,  then  a  single  cell,  or  the  inde- 
pendent homologue  of  a  single  cell,  having  no  other  to  co- 
operate with,  could  exhibit  no  structural  traits.  Not  only, 
however,  do  single-celled  organisms  exhibit  structural  traits, 
but  these,  even  among  the  simplest,  are  so  distinct  as  to 
originate  classification  into  orders,  genera,  and  species;  and 
they  are  so  constant  as  to  remain  the  same  from  generation 
to  generation. 

If,  then,  this  organic  polarity  (as  we  might  figuratively 
call  this  proclivity  towards  a  specific  structural  arrange- 
ment) can  be  possessed  neither  by  the  chemical  units  nor 
the  morphological  units,  we  must  conceive  it  as  possessed  by 
certain  intermediate  units,  which  we  may  term  physiological. 
There  seems  no  alternative  but  to  suppose  that  the  chemical 
units  combine  into  units  immensely  more  complex  than  them- 
selves, complex  as  they  are;  and  that  in  each  organism  the 
physiological  units  produced  by  this  further  compounding 
of  highly  compound  molecules,  have  a  more  or  less  distinc- 
tive character.  We  must  conclude  that  in  each  case  some 
difference  of  composition  in  the  units,  or  of  arrangement  in 
their  components,  leading  to  some  difference  in  their  mutual 
play  of  forces,  produces  a  difference  in  the  form  which  the 
aggregate  of  them  assumes. 

The  facts  contained  in  this  chapter  form  but  a  small  part 
of  the  evidence  which  thrusts  this  assumption  upon  us.  We 
shall  hereafter  find  various  reasons  for  inferring  that  such 
physiological  units  exist,  and  that  to  their  specific  properties, 
more  or  less  unlike  in  each  plant  and  animal,  various  organic 
phenomena  are  due. 


CHAPTER  V. 

ADAPTATION. 

§  67.  IN  plants  waste  and  repair  being  scarcely  appre- 
ciable, there  are  not  likely  to  arise  appreciable  changes  in  the 
proportions  of  already-formed  parts.  The  only  divergences 
from  the  average  structures  of  a  species,  which  we  may  expect 
particular  conditions  to  produce,  are  those  producible  by  the 
action  of  these  conditions  on  parts  in  course  of  formation; 
and  such  divergences  we  do  find.  We  know  that  a  tree 
which,  standing  alone  in  an  exposed  position,  has  a  short 
and  thick  stem,  has  a  tall  and  slender  stem  when  it  grows 
in  a  wood;  and  that  also  its  branches  then  take  a  different 
inclination.  We  know  that  potato-sprouts  which,  on  reaching 
the  light,  develop  into  foliage,  will,  in  the  absence  of  light, 
grow  to  a  length  of  several  feet  without  foliage.  And  every 
in-door  plant  furnishes  proof  that  shoots  and  leaves,  by 
habitually  turning  themselves  to  the  light,  exhibit  a  certain 
adaptation — an  adaptation  due,  as  we  must  suppose/  to  the 
special  effects  of  the  special  conditions  on  the  still  growing 
parts.  In  animals,  however,  besides  analogous  struc- 

tural changes  wrought  during  the  period  of  growth,  by  sub- 
jection to  circumstances  unlike  the  ordinary  circumstances, 
there  are  structural  changes  similarly  wrought  after  maturity 
has  been  reached.  Organs  that  have  arrived  at  their  full 
sizes  possess  a  certain  modifiability ;  so  that  while  the 

227 


228  THE  INDUCTIONS  OP  BIOLOGY. 

organism  as  a  whole  retains  pretty  nearly  the  same  bulk,  the 
proportions  of  its  parts  may  be  considerably  varied.  Their 
variations,  here  treated  of  under  the  title  Adaptation,  depend 
on  specialities  of  individual  action.  In  the  last  chapter  we 
saw  that  the  actions  of  organisms  entail  re-actions  on  them ; 
and  that  specialities  of  action  entail  specialities  of  re-action. 
Here  it  remains  to  be  pointed  out  that  these  special  actions 
and  re-actions  do  not  end  with  temporary  changes,  but  work 
permanent  changes. 

If,  in  an  adult  animal,  the  waste  and  repair  in  all  parts 
were  exactly  balanced — if  each  organ  daily  gained  by 
nutrition  exactly  as  much  as  it  lost  daily  by  the  discharge  of 
its  function — if  excess  of  function  were  followed  only  by 
such  excess  of  nutrition  as  balanced  the  extra  waste;  it  is 
clear  that  there  would  occur  no  change  in  the  relative  sizes 
of  organs.  But  there  is  no  such  exact  balance.  If  the  excess 
of  function,  and  consequent  excess  of  waste,  is  moderate,  it  is 
not  simply  compensated  by  repair  but  more  than  compensated 
— there  is  a  certain  increase  of  bulk.  This  is  true  to  some 
degree  of  the  organism  as  a  whole,  when  the  organism  is 
framed  for  activity.  A  considerable  waste  giving  considerable 
power  of  assimilation,  is  more  favourable  to  accumulation  of 
tissue  than  is  quiescence  with  its  comparatively  feeble  assimi- 
lation: whence  results  a  certain  adaptation  of  the  whole 
organism  to  its  requirements.  But  it  is  more  especially  true 
of  the  parts  of  an  organism  in  relation  to  one  another.  The 
illustrations  fall  into  several  groups.  The  growth 

of  muscles  exercised  to  an  unusual  degree  is  a  matter  of  com- 
mon observation.  In  the  often-cited  blacksmith's  arm,  the 
dancer's  legs  and  the  jockey's  crural  adductors,  we  have 
marked  examples  of  a  modifiability  which  almost  every  one 
has  to  some  extent  experienced.  It  is  needless  to  multiply 
proofs.  The  occurrence  of  changes  in  the  structure 

of  the  skin,  where  the  skin  is  exposed  to  unusual  stress  of 
function,  is  also  familiar.  That  thickening  of  the  epidermis 
on  a  labourer's  palm  results  from  continual  pressure  and 


ADAPTATION.  229 

friction,  is  certain.  Those  who  have  not  before  exerted  their 
hands,  find  that  such  an  exercise  as  rowing  soon  begins  to 
produce  a  like  thickening.  This  relation  of  cause  and  effect 
is  still  better  shown  by  the  marked  indurations  at  the  ends 
of  a  violinist's  fingers.  Even  in  mucous  membrane,  which 
ordinarily  is  not  subject  to  mechanical  forces  of  any  intensity, 
similar  modifications  are  possible:  witness  the  callosity  of 
the  gums  which  arises  in  those  who  have  lost  their  teeth, 
and  have  to  masticate  without  teeth.  The  vascular 

system  furnishes  good  instances  of  the  increased  growth  that 
follows  increased  function.  When,  because  of  some  perma- 
nent obstruction  to  the  circulation,  the  heart  has  to  exert  a 
greater  contractile  force  on  the  mass  of  blood  which  it 
propels  at  each  pulsation,  and  when  there  results  the  laboured 
action  known  as  palpitation,  there  usually  occurs  dilatation, 
or  hypertrophy,  or  a  mixture  of  the  two:  the  dilatation, 
which  is  a  yielding  of  the  heart's  structure  under  the  in- 
creased strain,  implying  a  failure  to  meet  the  emergency; 
but  the  hypertrophy,  which  consists  in  a  thickening  of  the 
heart's  muscular  walls,  being  an  adaptation  of  it  to  the 
additional  effort  required.  Again,  when  an  aneurism  in  some 
considerable  artery  has.  been  obliterated,  either  artifically 
or  by  a  natural  inflammatory  process;  and  when  this  artery 
has  consequently  ceased  to  be  a  channel  for  the  blood;  some 
of  the  adjacent  arteries  which  anastomose  with  it  become 
enlarged,  so  as  to  carry  the  needful  quantity  of  blood  to  the 
parts  supplied.  Though  we  have  no  direct  proof  of 

analogous  modifications  in  nervous  structures,  yet  indirect 
proof  is  given  by  the  greater  efficiency  that  follows  greater 
activity.  This  is  manifested  alike  in  the  senses  and  the 
intellect.  The  palate  may  be  cultivated  into  extreme  sensi- 
tiveness, as  in  professional  tea-tasters.  An  orchestral  con- 
ductor gains,  by  continual  practice,  an  unusually  great  ability 
to  discriminate  differences  of  sound.  In  the  finger-reading  of 
the  blind  we  have  evidence  that  the  sense  of  touch  may  be 
brought  by  exercise  to  a  far  higher  capability  than  is  ordi- 
10 


230  THE  INDUCTIONS  OF   BIOLOGY. 

nary.*  The  increase  of  power  which  habitual  exertion  gives 
to  mental  faculties  needs  no  illustration:  every  person  of 
education  has  personal  experience  of  it.  Even  from 

the  osseous  structures  evidence  may  be  drawn.  The  bones  of 
men  accustomed  to  great  muscular  action  are  more  massive, 
and  have  more  strongly  marked  processes  for  the  attachment 
of  muscles,  than  the  bones  of  men  who  lead  sedentary  lives; 
and  a  like  contrast  holds  between  the  bones  of  wild  and  tame 
animals  of  the  same  species.  Adaptations  of  another  order, 
in  which  there  is  a  qualitative  rather  than  a  quantitative 
modification,  arise  after  certain  accidents  to  which  the 
skeleton  is  liable.  When  the  hip-joint  has  been  dislocated, 
and  long  delay  has  made  it  impossible  to  restore  the  parts  to 
their  proper  places,  the  head  of  the  thigh-bone,  imbedded  in 
the  surrounding  muscles,  becomes  fixed  in  its  new  position 
by  attachments  of  fibrous  tissue,  which  afford  support  enough 
to  permit  a  halting  walk.  But  the  most  remarkable  modifi- 
cation of  this  order  occurs  in  united  ends  of  fractured 
bones.  "'  False  joints  "  are  often  formed — joints  which  rudely 
simulate  the  hinge  structure  or  the  ball-and-socket  structure, 
according  as  the  muscles  tend:  to  produce  a  motion  of  flexion 
and  extension  or  a  motion  of  rotation.  In  the  one  case, 
according  to  Rokitansky,  the  two  ends  of  the  broken  bone 
become  smooth  and  covered  with  periosteum  and  fibrous 
tissue,  and  are  attached  by  ligaments  that  allow  a  certain 
backward  and  forward  motion;  and  in  the  other  case  the 
ends,  similarly  clothed  with  the  appropriate  membranes, 
become  the  one  convex  and  the  other  concave,  are  inclosed 
in  a  capsule,  and  are  even  occasionally  supplied  with  syno- 
vial  fluid ! 

The  general  truth  that  extra  function  is  followed  by  extra 
growth,  must  be  supplemented  by  the  equally  general  truth, 

*  In  the  account  of  James  Mitchell,  a  boy  born  blind  and  deaf,  given  by 
James  Wardrop,  F.  R.S.  (Edin.  1813),  it  is  said  that  he  acquired  a  "preter- 
natural acuteness  of  touch  and  smell."  The  deaf  Dr.  Kitto  described  him- 
self as  having  an  extremely  strong  visual  memory:  he  retained  "a  clear 
impression  or  image  of  everything.at  which  he  ever  looked." 


ADAPTATION".  231 

that  beyond  a  limit,  usually  soon  reached,  very  little,  if  any, 
further  modification  can  be  produced.  The  experiences  which 
we  colligate  into  the  one  induction  thrust  the  other  upon  us. 
After  a  time  no  training  makes  the  pugilist  or  the  athlete 
any  stronger.  The  adult  gymnast  at  last  acquires  the  power 
to  perform  certain  difficult  feats;  but  certain  more  difficult 
feats  no  additional  practice  enables  him  to  perform.  Years  of 
discipline  give  the  singer  a  particular  loudness  and  range  of 
voice,  beyond  which  further  discipline  does  not  give  greater 
loudness  or  wider  range:  on  the  contrary,  increased  vocal 
exercise,  causing  a  waste  in  excess  of  repair,  is  often  followed 
by  decrease  of  power.  In  the  exaltation  of  the  per- 

ceptions we  see  similar  limits.  The  culture  which  raises 
the  susceptibility  of  the  ear  to  the  intervals  and  harmonies 
of  notes,  will  not  turn  a  bad  ear  into  a  good  one.  Life- 
long effort  fails  to  make  this  artist  a  correct  draftsman  or 
that  a  fine  colourist:  each  does  better  than  he  did  at  first, 
but  each  falls  short  of  the  power  attained  by  some  other 
artists.  ISTor  is  this  truth  less  clearly  illustrated 

among  the  more  complex  mental  powers.  A  man  may  have 
a  mathematical  faculty,  a  poetical  faculty,  or  an  oratorical 
faculty,  which  special  education  improves  to  a  certain  extent. 
But  unless  he  is  unusually  endowed  in  one  of  those  directions, 
no  amount  of  education  will  make  him  a  first-rate  mathe- 
matician, a  first-rate  poet,  or  a  first-rate  orator.  Thus 
the  general  fact  appears  to  be  that  while  in  each  individual 
certain  changes  in  the  proportions  of  parts  may  be  caused 
by  variations  of  functions,  the  congenital  structure  of  each 
individual  puts  a  limit  to  the  modifiability  of  every 
part.  Nor  is  this  true  of  individuals  only :  it  holds, 
in  a  sense,  of  species.  Leaving  open  the  question  whether, 
in  indefinite  times,  indefinite  modifications  may  not  be  pro- 
duced by  inheritance  of  functionally  wrought  adaptations; 
experience  proves  that  within  assigned  times,  the  changes 
wrought  in  races  of  organisms  by  changes  .of  conditions  fall 
within  narrow  limits.  Though  by  discipline,  aided  by  selec- 


232  THE  INDUCTIONS  OF  BIOLOGY. 

tivc  breeding,  one  variety  of  horse  has  had  its  locomotive 
power  increased  considerably  beyond  the  locomotive  powers 
of  other  varieties;  yet  further  increase  takes  place,  if  at  all, 
at  an  inappreciable  rate.  The  different  kinds  of  dogs,  too,  in 
which  different  forms  and  capacities  have  been  established, 
do  not  now  show  aptitudes  for  diverging  in  the  same  direc- 
tions at  considerable  rates.  In  domestic  animals  generally, 
certain  accessions  of  intelligence  have  been  produced  by 
culture;  but  accessions  beyond  these  are  inconspicuous.  It 
seems  that  in  each  species  of  organism  there  is  a  margin  for 
functional  oscillations  on  all  sides  of  a  mean  state,  and  a  con- 
sequent margin  for  structural  variations;  that  it  is  possible 
rapidly  to  push  functional  and  structural  changes  towards 
the  extreme  of  this  margin  in  any  direction,  both  in  an  indi- 
vidual and  in  a  race;  but  that  to  push  these  changes  further 
in  any  direction,  and  so  to  alter  the  organism  as  to  bring  its 
mean  state  up  to  the  extreme  of  the  margin  in  that  direction, 
is  a  comparatively  slow  process.* 

We  also  have  to  note  that  the  limited  increase  of  size  pro- 
duced in  any  organ  by  a  limited  increase  of  its  function,  is 
not  maintained  unless  the  increase  of  function  is  permanent. 
A  mature  man  or  other  animal,  led  by  circumstances  into 
exerting  particular  members  in  unusual  degrees,  and  acquir- 
ing extra  sizes  in  these  members,  begins  to  lose  such  extra 
sizes  on  ceasing  to  exert  the  members;  and  eventually  lapses 
more  or  less  nearly  into  the  original  state.  Legs  strength- 
ened by  a  pedestrian  tour,  become  relatively  weak  again  after 
a  prolonged  return  to  sedentary  life.  The  acquired  ability  to 
perform  feats  of  skill  disappears  in  course  of  time,  if  the  per- 
formance of  them  be  given  up.  For  comparative  failure  in 
executing  a  piece  of  music,  in  playing  a  game  at  chess,  or  in 
anything  requiring  special  culture,  the  being  out  of  practice 

*  Here,  as  in  sundry  places  throughout  this  chapter,  the  necessities  of  the 
argument  have  obliged  me  to  forestall  myself,  by  assuming  the  conclusion 
reached  in  a  subsequent  chapter,  that  modifications  of  structure  produced  by 
modifications  of  function  are  transmitted  to  offspring. 


ADAPTATION.  233 

is  a  reason  which  every  one  recognizes  as  valid.  It  is  ob- 
servable, too,  that  the  rapidity  and  completeness  with  which 
an  artificial  power  is  lost,  is  proportionate  to  the  shortness  of 
the  cultivation  which  evoked  it.  One  who  has  for  many 
years  persevered  in  habits  which  exercise  special  muscles  or 
special  faculties  of  mind,  retains  the  extra  capacity  produced, 
to  a  very  considerable  degree,  even  after  a  long  period  of 
dcsistance;  but  one  who  has  persevered  in  such  habits  for 
but  a  short  time  has,  at  the  end  of  a  like  period,  scarcely  any 
of  the  facility  he  had  gained.  Here  too,  as  before,  suc- 

cessions of  organisms  present  an  analogous  fact.  A  species 
in  which  domestication  continued  through  many  generations, 
has  organized  certain  peculiarities;  and  which  afterwards, 
escaping  domestic  discipline,  returns  to  something  like  its 
original  habits;  soon  loses,  in  great  measure,  such  peculiari- 
ties. Though  it  is  not  true,  as  alleged,  that  it  resumes  com- 
pletely the  structure  it  had  before  domestication,  yet  it 
approximates  to  that  structure.  The  Dingo,  or  wild  dog  of 
Australia,  is  one  of  the  instances  given  of  this;  and  the  wild 
horse  of  South  America  is  another.  Mankind,  too,  supplies 
us  with  instances.  In  the  Australian  bush  and  in  the  back- 
woods of  America,  the  Anglo-Saxon  race,  in  which  civilization 
has  developed  the  higher  feelings  to  a  considerable  degree, 
rapidly  lapses  into  comparative  barbarism:  adopting  the 
moral  code,  and  sometimes  the  habits,  of  savages. 

§  68.  It  is  important  to  reach,  if  possible,  some  rationale 
of  these  general  truths — especially  of  the  last  two.  A  right 
understanding  of  these  laws  of  organic  modification  underlies 
a  right  understanding  of  the  great  question  of  species.  While, 
as  before  hinted  (§40),  the  action  of  structure  on  function 
is  one  of  the  factors  in  that  process  of  differentiation  by 
which  unlike  forms  of  plants  and  animals  are  produced,  the 
reaction  of  function  on  structure  is  another  factor.  Hence, 
it  is  well  worth  while  inquiring  how  far  these  inductions  are 
deductively  interpretable. 


234  THE  INDUCTIONS  OF  BIOLOGY. 

The  first  of  them  is  the  most  difficult  to  deal  with.  Why 
an  organ  exerted  somewhat  beyond  its  wont  should  presently 
grow,  and  thus  meet  increase  of  demand  by  increase  of  sup- 
ply, is  not  obvious.  We  know,  indeed,  (First  Principles, 
§§  85,  173,)  that  of  necessity,  the  rhythmical  changes  pro- 
duced by  antagonistic  organic  actions  cannot  any  of  them  be 
carried  to  an  excess  in  one  direction,  without  there  being 
produced  an  equivalent  excess  in  the  opposite  direction.  It 
is  a  corollary  from  the  persistence  of  force,  that  any  deviation 
effected  by  a  disturbing  cause,  acting  on  some  member  of  a 
moving  equilibrium,  must  (unless  it  altogether  destroys  the 
moving  equilibrium)  be  eventually  followed  by  a  compensat- 
ing deviation.  Hence,  that  excess  of  repair  should  succeed  ex- 
cess of  waste,  is  to  be  expected.  But  how  happens  the  mean 
state  of  the  organ  to  be  changed?  If  daily  extra  waste 
naturally  brings  about  daily  extra  repair  only  to  an  equiva- 
lent extent,  the  mean  state  of  the  organ  should  remain  con- 
stant. How  then  comes  the  organ  to  augment  in  size  and 
power  ? 

Such  answer  to  this  question  as  we  may  hope  to  find,  must 
be  looked  for  in  the  effects  wrought  on  the  organism  as  a 
whole  by  increased  function  in  one  of  its  parts.  For  since 
the  discharge  of  its  function  by  any  part  is  possible  only  on 
condition  that  those  various  other  functions  on  which  its  own 
is  immediately  dependent  are  also  discharged,  it  follows  that 
excess  in  its  function  presupposes  some  excess  in  their  func- 
tions. Additional  work  given  to  a  muscle  implies  additional 
work  given  to  the  branch  arteries  which  bring  it  blood,  and 
additional  work,  smaller  in  proportion,  to  the  arteries  from 
which  these  branch  arteries  come.  Similarly,  the  smaller 
and  larger  veins  which  take  away  the  blood,  as  well  as  those 
structures  which  deal  with  effete  products,  must  have  more 
to  do.  And  yet  further,  on  the  nervous  centres  which  excite 
the  muscle  a  certain  extra  duty  must  fall.  But  excess  of 
waste  will  entail  excess  of  repair,  in  these  parts  as  well  as  in 
the  muscle.  The  several  appliances  by  which  the  nutrition 


ADAPTATION.  235 

and  excitation  of  an  organ  are  carried  on,  must  also  be  in- 
fluenced by  this  rhythm  of  action  and  reaction;  and  there- 
fore, after  losing  more  than  usual  by  the  destructive  process 
they  must  gain  more  than  usual  by  the  constructive  process. 
But  temporarily-increased  efficiency  in  these  appliances  by 
which  blood  and  nervous  force  are  brought  to  an  organ,  will 
cause  extra  assimilation  in  the  organ,  beyond  that  required  to 
balance  its  extra  expenditure.  Regarding  the  functions  as 
constituting  a  moving  equilibrium,  we  may  say  that  diverg- 
ence of  any  function  in  the  direction  of  increase,  causes  the 
functions  with  which  it  is  bound  up  to  diverge  in  the  same 
direction;  that  these,  again,  cause  the  functions  which  they 
are  bound  up  with,  also  to  diverge  in  the  same  direction ;  and 
that  these  divergences  of  the  connected  functions  allow  the 
specially-affected  function  to  be  carried  further  in  this  direc- 
tion than  it  could  otherwise  be — further  than  the  perturbing 
force  could  carry  it  if  it  had  a  fixed  basis. 

It  must  be  admitted  that  this  is  but  a  vague  explanation. 
Among  actions  so  involved  as  these,  we  can  scarcely  expect 
to  do  more  than  dimly  discern  a  harmony  with  first  princi- 
ples. That  the  facts  are  to  be  interpreted  in  some  such  way, 
may,  how«ver,  be  inferred  from  the  circumstance  that  an 
extra  supply  of  blood  continues  for  some  time  to  be  sent  to 
an  organ  that  has  been  unusually  exercised;  and  that  when 
unusual  exercise  is  long  continued  a  permanent  increase  of 
vascularity  results. 

§  69.  Answers  to  the  questions — Why  do  these  adaptive 
modifications  in  an  individual  animal  soon  reach  a  limit? 
and  why,  in  the  descendants  of  such  animal,  similarly  condi- 
tioned, is  this  limit  very  slowly  extended? — are  to  be  found 
in  the  same  direction  as  was  the  answer  to  the  last  question. 
And  here  the  connexion  of  cause  and  consequence  is  more 
manifest. 

Since  the  function  of  any  organ  is  dependent  on  the  func- 
tions of  the  organs  which  supply  it  with  materials  and 


2,3G  THE   INDUCTIONS  OP  BIOLOGY. 

stimuli;  and  since  the  functions  of  these  subsidiary  organs 
are  dependent  on  the  functions  of  organs  which  supply  them 
with  materials  and  stimuli;  it  follows  that  before  any  great 
extra  power  of  discharging  its  function  can  be  gained  by  a 
specially-exercised  organ,  a  considerable  extra  power  must 
be  gained  by  a  series  of  immediately-subservient  organs,  and 
some  extra  power  by  a  secondary  series  of  remotely-sub- 
servient organs.  Thus  there  are  required  numerous  and 
wide-spread  modifications.  Before  the  artery  which  feeds  a 
hard-worked  muscle  can  permanently  furnish  a  large  addi- 
tional quantity  of  blood,  it  must  increase  in  diameter;  and 
that  its  increase  of  diameter  may  be  of  use,  the  main  artery 
from  which  it  diverges  must  also  be  so  far  modified  as  to 
bring  this  additional  quantity  of  blood  to  the  branch  artery. 
Similarly  with  the  veins ;  similarly  with  the  structures  which 
remove  waste-products;  similarly  with  the  nerves.  And 
when  we  ask  what  these  subsidiary  changes  imply,  we  are 
forced  to  conclude  that  there  must  be  an  analogous  group  of 
more  numerous  changes  ramifying  throughout  the  system. 
The  growth  of  the  arteries  primarily  and  secondarily  im- 
plicated, cannot  go  to  any  extent  without  growth  in  the 
minor  blood-vessels  on  which  their  nutrition  depends;  while 
their  greater  contractile  power  involves  enlargement  of  the 
nerves  which  excite  them,  and  some  modification  of  that  part 
of  the  spinal  cord  whence  these  nerves  proceed.  Thus,  with- 
out tracing  the  like  remote  alterations  implied  by  extra 
growth  of  the  veins,  lymphatics,  glandular  organs,  and  other 
agencies,  it  is  manifest  that  a  large  amount  of  rebuilding 
must  be  done  throughout  the  organism,  before  any  organ  of 
importance  can  be  permanently  increased  in  size  and  power 
to  a  great  extent.  Hence,  though  such  extra  growth  in  any 
part  as  does  not  necessitate  considerable  changes  throughout 
the  rest  of  the  organism,  may  rapidly  take  place;  a  further 
growth  in  this  part,  requiring  a  re-modelling  of  numerous 
parts  remotely  and  slightly  affected,  must  take  place  but 
slowly. 


ADAPTATION.  237 

We  have  before  found  our  conceptions  of  vital  processes 
made  clearer  by  studying  analogous  social  processes.  In 
societies  there  is  a  mutual  dependence  of  functions,  essen- 
tially like  that  which  exists  in  organisms;  and  there  is  also 
an  essentially  like  reaction  of  functions  on  structures. 
From  the  laws  of  adaptive  modification  in  societies,  we  may 
therefore  hope  to  get  a  clue  to  the  laws  of  adaptive  modifi- 
cation in  organisms.  Let  us  suppose,  then,  that  a 
society  has  arrived  at  a  state  of  equilibrium  analogous  to 
that  of  a  mature  animal — a  state  not  like  our  own,  in  which 
growth  and  structural  development  are  rapidly  going  on,  but 
a  state  of  settled  balance  among  the  functional  powers  of  the 
various  classes  and  industrial  bodies,  and  a  consequent  fixity 
in  the  relative  sizes  of  such  classes  and  bodies.  Further, 
let  us  suppose  that  in  a  society  thus  balanced  there  occurs 
something  which  throws  an  unusual  demand  on  one  industry 
— say  an  unusual  demand  for  ships  (which  we  will  assume  to 
be  built  of  iron)  in  consequence  of  a  competing  mercantile 
nation  having  been  prostrated  by  famine  or  pestilence.  The 
immediate  result  of  this  additional  demand  for  iron  ships  is 
the  employment  of  more  workmen,  and  the  purchase  of  more 
iron,  by  the  ship-builders;  and  when,  presently,  the  demand 
continuing,  the  ship-builders  find  their  premises  and  machi- 
nery insufficient,  they  enlarge  them.  If  the  extra  require- 
ment persists,  the  high  interest  and  high  wages  bring  such 
extra  capital  and  labour  into  the  business  as  are  needed  for 
new  ship-building  establishments.  But  such  extra  capital 
and  labour  do  not  come  quickly;  since,  in  a  balanced  com- 
munity, not  increasing  in  population  and  wealth,  labour  and 
capital  have  to  be  drawn  from  other  industries,  where  they 
are  already  yielding  the  ordinary  returns.  Let  us 
now  go  a  step  further.  Suppose  that  this  iron-ship-building 
industry,  having  enlarged  as  much  as  the  available  capital 
and  labour  permit,  is  still  unequal  to  the  demand;  what 
limits  its  immediate  further  growth?  The  lack  of  iron. 
By  the  hypothesis,  the  iron-producing  industry,  like  all  the 


238  THE  INDUCTIONS  OF  BIOLOGY. 

other  industries  throughout  the  community,  yields  only 
as  much  iron  as  is  habitually  required  for  all  the  pur- 
poses to  which  iron  is  applied:  ship-building  being  only 
one.  If,  then,  extra  iron  is  required  for  ship-building,  the 
first  effect  is  to  withdraw  part  of  the  iron  habitually  con- 
sumed for  other  purposes,  and  to  raise  the  price  of  iron. 
Presently,  the  iron-makers  feel  this  change  and  their  stocks 
dwindle.  As,  however,  the  quantity  of  iron  required  for 
ship-building  forms  but  a  small  part  of  the  total  quantity 
required  for  all  purposes,  the  extra  demand  on  the  iron- 
makers  can  be  nothing  like  so  great  in  proportion  as  is  the 
extra  demand  on  the  ship-builders.  Whence  it  follows  that 
there  will  be  much  less  tendency  to  an  immediate  enlarge- 
ment of  the  iron-producing  industry;  since  the  extra  quan- 
tity will  for  some  time  be  obtained  by  working  extra  hours. 
Nevertheless  if,  as  fast  as  more  iron  can  be  thus  supplied, 
the  ship-building  industry  goes  on  growing — if,  consequently, 
the  iron-makers  experience  a  permanently-increased  demand, 
and  out  of  their  greater  profits  get  higher  interest  on  capital, 
as  well  as  pay  higher  wages;  there  will  eventually  be  an 
abstraction  of  capital  and  labour  from  other  industries  to 
enlarge  the  iron-producing  industry:  new  blast-furnaces, 
new  rolling-mills,  new  cottages  for  workmen,  will  be  erected. 
But  obviously,  the  inertia  of  capital  and  labour  to  be  over- 
come before  the  iron-producing  industry  can  grow  by  a 
decrease  of  certain  other  industries,  will  prevent  its  growth 
from  taking  place  until  long  after  the  increased  ship-building 
industry  has  demanded  it ;  and  meanwhile,  the  growth  of  the 
ship-building  industry  must  be  limited  by  the  deficiency  of 
iron.  A  remoter  restraint  of  the  same  nature  meets 

us  if  we  go  a  step  further — a  restraint  which  can  be  over- 
come only  in  a  still  longer  time.  For  the  manufacture  of 
iron  depends  on  the  supply  of  coal.  The  production  of  coal 
being  previously  in  equilibrium  with  the  consumption;  and 
the  consumption  of  coal  for  the  manufacture  of  iron  being 
but  a  small  part  of  the  total  consumption;  it  follows  that  a 


ADAPTATION.  239 

considerable  extension  of  the  iron  manufacture,  when  it  at 
length  takes  place,  will  cause  but  a  comparatively  small 
additional  demand  on  the  coal-owners  and  coal-miners — a 
demand  which  will  nqt,  for  a  long  period,  suffice  to  cause 
enlargement  of  the  coal-trade,  by  drawing  capital  and  labour 
from  other  investments  and  occupations.  And  until  the  per- 
manent extra  demand  for  coal  has  become  great  enough  to 
draw  from  other  investments  and  occupations  sufficient 
capital  and  labour  to  sink  new  mines,  the  increasing  produc- 
tion of  iron  must  be  restricted  by  the  scarcity  of  coal,  and 
the  multiplication  of  ship-yards  and  ship-builders  must  be 
checked  by  the  want  of  iron.  Thus,  in  a  community  which 
has  reached  a  state  of  moving  equilibrium,  though  any  one 
industry  directly  affected  by  an  additional  demand  may 
rapidly  undergo  a  small  extra  growth,  yet  a  growth  beyond 
this,  requiring  as  it  does  the  building-up  of  subservient  in- 
dustries, less  directly  and  strongly  affected,  as  well  as  the 
partial  unbuilding  of  other  industries,  can  take  place  only 
with  comparative  slowness.  And  a  still  further  growth,  re- 
quiring structural  modifications  of  industries  still  more  dis- 
tantly affected,  must  take  place  still  more  slowly. 

On  returning  from  this  analogy,  we  see  more  clearly  the 
truth  that  any  considerable  member  of  an  animal  organism, 
cannot  be  greatly  enlarged  without  some  general  reorganiza- 
tion. Besides  a  building  up  of  the  primary,  secondary,  and 
tertiary  groups  of  the  subservient  parts,  there  must  be  an  un- 
building of  sundry  non-subservient  parts;  or,  at  any  rate, 
there  must  be  permanently  established  a  lower  nutrition  of 
such  non-subservient  parts.  For  it  must  be  remembered  that 
in  a  mature  animal,  or  one  which  has  reached  a  balance 
between  assimilation  and  expenditure,  there  cannot  (suppos- 
ing general  conditions  to  remain  constant)  be  an  increase  in 
the  nutrition  of  some  organs  without  a  decrease  in  the  nutri- 
tion of  others;  and  an  organic  establishment  of  the  increase 
implies  an  organic  establishment  of  the  decrease — implies 
more  or  less  change  in  the  processes  and  structures  through- 


240  THE  INDUCTIONS  OP   BIOLOGV. 

out  the  entire -system.  And  here,  indeed,  is  disclosed 

one  reason  why  growing  animals  undergo  adaptations  so  much 
more  readily  than  adult  ones.  For  while  there  is  surplus 
nutrition,  it  is  possible  for  specially-exercised  parts  to  be 
specially  enlarged  without  any  positive  deduction  from  other 
parts.  There  is  required  only  that  negative  deduction  implied 
in  the  diminished  growth  of  other  parts. 

§  70.  Pursuing  the  argument  further,  we  reach  an  ex- 
planation of  the  third  general  truth;  namely  that  organisms, 
and  species  of  organisms,  which,  under  new  conditions,  have 
undergone  adaptive  modifications,  soon  return  to  something 
like  their  original  structures  when  restored  to  their  original 
conditions.  Seeing,  as  we  have  done,  how  excess  of  action 
and  excess  of  nutrition  in  any  part  of  an  organism,  must 
affect  action  and  nutrition  in  subservient  parts,  and  these 
again  in  other  parts,  until  the  re-action  has  divided  and 
subdivided  itself  throughout  the  organism,  affecting  in 
decreasing  degrees  the  more  and  more  numerous  parts  more 
and  more  remotely  implicated;  we  see  that  the  consequent 
changes  in  the  parts  remotely  implicated,  constituting  the 
great  mass  of  the  organism,  must  be  extremely  slow.  Hence, 
if  the  need  for  the  adaptive  modification  ceases  before  the 
great  mass  of  the  organism  has  been  much  altered  in  its 
structure  by  these  ramified  but  minute  reactions,  we  shall 
have  a  condition  in  which  the  specially-modified  part  is  not 
in  equilibrium  with  the  rest.  All  the  remotely-affected 
organs,  as  yet  but  little  changed,  will,  in  the  absence  of  the 
perturbing  cause,  resume  very  nearly  their  previous  actions. 
The  parts  that  depend  on  them  will  consequently  by  and  by 
do  the  same.  Until  at  length,  by  a  reversal  of  the  adaptive 
process,'  the  organ  at  first  affected  will  be  brought  back 
almost  to  its  original  state.  Eeconsidering  the 

above-drawn  analogy  between  an  organism  and  a  society,  will 
enable  us  better  to  recognize  this  necessity.  If,  in  the  case 
supposed,  the  extra  demand  for  iron  ships,  after  causing 


ADAPTATION.  241 

the  erection  of  some  additional  ship-yards  and  the  drawing 
of  iron  from  other  manufactures,  were  to  cease;  the  old 
dimensions  of  the  ship-building  trade  would  be  quickly  re- 
turned to:  discharged  workmen  would  seek  fresh  occupa- 
tions, and  the  new  yards  would  be  devoted  to  other  uses. 
But  if  the  increased  need  for  ships  lasted  long  enough,  and 
became  great  enough,  to  cause  a  flow  of  capital  and  labour 
from  other  industries  into  the  iron-manufacture,  a  falling  off 
in  the  demand  for  ships,  would  much  less  rapidly  entail  a 
dwindling  of  the  ship-building  industry.  For  iron  being 
now  produced  in  greater  quantity,  a  diminished  consumption 
of  it  for  ships  would  cause  a  fall  in  its  •  price,  and  a  conse- 
quent fall  in  the  cost  of  ships:  thus  enabling  the  ship- 
builders to  meet  the  competition  which  we  may  suppose  led 
to  a  decrease  in  the  orders  they  received.  And  since,  when 
new  blast-furnaces  and  rolling-mills,  &c.,  had  been  built 
with  capital  drawn  from  other  industries,  its  transference 
back  into  other  industries  would  involve  great  loss;  the 
owners,  rather  than  transfer  it,  would  accept  unusually  low 
interest,  and  an  excess  of  iron  would  continue  to  be  produced ; 
resulting  in  an  undue  cheapness  of  ships,  and  a  maintenance 
of  the  ship-building  industry  at  a  size  beyond  the  need. 
Event  .lally,  however,  if  the  number  of  ships  required  still 
diminished,  the  production  of  iron  in  excess  would  become 
very  unremunerative :  some  of  the  blast-furnaces  would  be 
blown  out ;  and  as  much  of  the  capital  and  labour  as  remained 
available  would  be  re-distributed  among  other  occupations. 
Without  repeating  the  steps  of  the  argument,  it  will  be  clear 
that  were  the  enlargement  of  the  ship-building  industry  great 
enough,  and  did  it  last  long  enough  to  cause  an  increase  in 
the  number  of  coal-mines,  the  ship-building  industry  would 
be  still  better  able  to  maintain  itself  under  adverse  circum- 
stances ;  but  that  it  would,  though  at  a  more  distant  period, 
end  by  sinking  down  to  the  needful  dimensions.  Thus  our 
conclusions  are: — First,  that  if  the  extra  growth  caused  by 
extra  activity  in  a  particular  industry  has  lasted  long  enough 


242  THE  INDUCTIONS  OP  BIOLOGY. 

only  to  remodel  the  proximately-affected  industries;  it  will 
dwindle  away  again  after  a  moderate  period,  if  the  need  for 
it  disappears.  Second,  that  a  long  period  must  be  required 
before  the  re-actions  produced  by  an  enlarged  industry  can 
cause  a  re-construction  of  the  whole  society,  and  before  the 
countless  re-distributions  of  capital  and  labour  can  again 
reach  a  state  of  equilibrium.  And  third,  that  only  when 
such  a  new  state  of  equilibrium  is  eventually  reached,  can  the 
adaptive  modification  become  a  permanent  one.  How, 

in  animal  organisms  the  like  argument  holds,  need  not  be 
pointed  out.  The  reader  will  readily  follow  the  parallel. 

That  organic  types  should  be  comparatively  stable,  might 
be  anticipated  on  the  hypothesis  of  Evolution.  The  structure 
of  any  organism  being  a  product  of  the  almost  infinite  series 
of  actions  and  reactions  to  which  ancestral  organisms  have 
been  exposed;  any  unusual  actions  and  reactions  brought  to 
bear  on  an  individual,  can  have  but  an  infinitesimal  effect  in 
permanently  changing  the  structure  of  the  organism  as  a 
whole.  The  new  set  of  forces,  compounded  with  all  the  an- 
tecedent sets  of  forces,  can  but  inappreciably  modify  that 
moving  equilibrium  of  functions  which  all  these  antecedent 
sets  of  forces  have  established.  Though  there  may  result  a 
considerable  perturbation  of  certain  functions — a  considerable 
divergence  from  their  ordinary  rhythms — yet  the  general  centre 
of  equilibrium  cannot  be  sensibly  changed.  On  the  removal 
of  the  perturbing  cause  the  previous  balance  will  be  quickly 
restored :  the  effect  of  the  new  forces  being  almost  obliterated 
by  the  enormous  aggregate  of  forces  which  the  previous 
balance  expresses. 

§  71.  As  thus  understood,  the  phenomena  of  adaptation 
fall  into  harmony  with  first  principles.  The  inference  that 
organic  types  are  fixed,  because  the  deviations  from  them 
which  can  be  produced  within  assignable  periods  are  relatively 
small,  and  because,  when  a  force  producing  deviation  ceases, 
there  is  a  return  to  something  like  the  original  state ;  proves  to 


ADAPTATION.  243 

be  an  invalid  inference.  Without  assuming  fixity  of  species, 
we  find  good  reasons  for  anticipating  that  kind  and  degree  of 
stability  which  is  observed.  We  find  grounds  for  concluding, 
a  priori,  that  an  adaptive  change  of  structure  will  soon  reach 
a  point  beyond  which  further  adaptation  will  be  slow;  for 
concluding  that  when  the  modifying  cause  has  been  but 
a  short  time  in  action,  the  modification  generated  will  be 
evanescent;  for  concluding  that  a  modifying  cause  acting 
even  for  many  generations,  will  do  but  little  towards  per- 
manently altering  the  organic  equilibrium  of  a  race ;  and  for 
concluding  that  on  the  cessations  of  such  cause,  its  effects 
will  become  unapparent  in  the  course  of  a  few  generations. 


CHAPTEE  VI. 

INDIVIDUALITY. 

§  72.  WHAT  is  an  individual  ?  is  a  question  which  many 
readers  will  think  it  easy  to  answer.  Yet  it  is  a  question 
that  has  led  to  much  controversy  among  Zoologists  and 
Botanists,  and  no  quite  satisfactory  reply  to  it  seems  possible. 
As  applied  to  a  man,  or  to, any  one  of  the  higher  animals, 
which  are  all  sharply-defined  and  independent,  the  word  in- 
dividual has  a  clear  meaning:  though  even  here,  when  we 
turn  from  average  cases  to  exceptional  cases — as  a  calf  with 
two  heads  and  two  pairs  of  fore-limbs — we  find  ourselves  in 
doubt  whether  to  predicate  one  individuality  or  two.  But 
when  we  extend  our  range  of  observation  to  the  organic  world 
at  large,  we  find  that  difficulties  allied  to  this  exceptional 
one  meets  us  everywhere  under  every  variety  of  form. 

Each  uniaxial  plant  may  perhaps  fairly  be  regarded  as  a 
distinct  individual;  though  there  are  botanists  who  do  not 
make  even  this  admission.  What,  however,  are  we  to  say  of 
a  multiaxial  plant?  It  is,  indeed,  usual  to  speak  of  a  tree 
with  its  many  branches  and  shoots  as  singular;  but  strong 
reasons  may  be  urged  for  considering  it  as  plural.  Every 
one  of  its  axes  has  a  more  or  less  independent  life,  and  when 
cut  off  and  planted  may  grow  into  the  likeness  of  its  parent ; 
or,  by  grafting  and  budding,  parts  of  this  tree  may  be 
developed  upon  another  tree,  and  there  manifest  their 
specific  peculiarities.  Shall  we  regard  all  the  growing  axes 
thus  resulting  from  slips  and  grafts  and  buds,  as  parts  of  one 
244 


INDIVIDUALITY.  245 

individual  or  as  distinct  individuals?  If  a  strawberry-plant 
sends  out  runners  carrying  buds  at  their  ends,  which  strike 
root  and  grow  into  independent  plants  that  separate  from 
the  original  one  by  decay  of  the  runners,  must  we  not  say 
that  they  possess  separate  individualities;  and  yet  if  we  do 
this,  are  we  not  at  a  loss  to  say  when  their  separate  individu- 
alities were  established,  unless  we  admit  that  each  bud  was 
from  the  beginning  an  individual?  Commenting  on  such 
perplexities  Schleiden  says — "  Much  has  been  written  and 
disputed  concerning  the  conception  of  the  individual,  without, 
however,  elucidating  the  subject,  principally  owing  to  the 
misconception  that  still  exists  as  to  the  origin  of  the  concep- 
tion. Now  the  individual  is  no  conception,  but  the  mere 
subjective  comprehension  of  an  actual  object,  presented  to  us 
under  some  given  specific  conception,  and  on  this  latter  it 
alone  depends  whether  the  object  is  or  is  not  an  individual. 
Under  the  specific  conception  of  the  solar  system,  ours  is  an 
individual :  in  relation  to  the  specific  conception  of  a  planetary 
body,  it  is  an  aggregate  of  many  individuals."  ..."  I 
think,  however,  that  looking  at  the  indubitable  facts  already 
mentioned,  and  the  relations  treated  of  in  the  course  of 
these  considerations,  it  will  appear  most  advantageous  and 
most  useful,  in  a  scientific  point  of  view,  to  consider  the 
vegetable  cell  as  the  general  type  of  the  plant  (simple  plant 
of  the  first  order).  Under  this  conception,  Protococcus  and 
other  plants  consisting  of  only  one  cell,  and  the  spore  and 
pollen-granule,  will  appear  as  individuals.  Such  individuals 
may,  however,  again,  with  a  partial  renunciation  of  their  in" 
dividual  independence,  combine  under  definite  laws  into 
definite  forms  (somewhat  as  the  individual  animals  do  in  the 
globe  of  the  Volvox  globator  *).  These  again  appear  empiri- 
cally as  individual  beings,  under  a  conception  of  a  species 
(simple  plants  of  the  second  order)  derived  from  the  form  of 

*  Whether  the  Volvox  is  to  be  classed  as  animal  or  vegetal  is  a  matter  of 
dispute ;  but  its  similarity  to  the  blastula  stage  of  many  animals  warrants  the 
claim  of  the  zoologists. 


246  THE  INDUCTIONS  OP   BIOLOGY. 

the  normal  connexion  of  the  elementary  individuals.  But 
we  cannot  stop  here,  since  Nature  herself  combines  these 
individuals,  under  a  definite  form,  into  larger  associations, 
whence  we  draw  the  third  conception  of  the  plant,  from  a 
connexion,  as  it  were,  of  the  second  power  (compound  plants 
— plants  of  the  third  order).  The  simple  plant  proceeding 
from  the  combination  of  the  elementary  individuals  is  then 
termed  a  bud  (gemma),  in  the  composition  of  plants  of  the 
third  order." 

The  animal  kingdom  presents  still  greater  difficulties. 
When,  from  sundry  points  on  the  body  of  a  common  polype, 
there  bud  out  young  polypes  which,  after  acquiring  mouths 
and  tentacles  and  closing  up  the  communications  between 
their  stomachs  and  the  stomach  of  the  parent,  finally  separate 
from  the  parent;  we  may  with  propriety  regard  them  as 
distinct  individuals.  But  when  in  the  allied  compound 
Hydrozoa,  we  find  that  these  young  polypes  continue  per- 
manently connected  with  the  parent;  and  when  by  this 
continuous  budding-out  there  is  presently  produced  a  tree- 
like aggregation,  having  a  common  alimentary  canal  into 
which  the  digestive  cavity  of  each  polype  opens;  it  is  no 
longer  so  clear  that  these  little  sacs,  furnished  with  mouths 
and  tentacles,  are  severally  to  be  regarded  as  distinct  indi- 
viduals. We  cannot  deny  a  certain  individuality  to  the 
polypedom.  And  on  discovering  that  some  of  the  buds, 
instead  of  unfolding  in  the  same  manner  as  the  rest,  are 
transformed  into  capsules  in  which  eggs  are  developed — on 
discovering  that  certain  of  the  incipient  polypes  thus  become 
wholly  dependent  on  the  aggregate  for  their  nutrition,  and 
discharge  functions  which  have  nothing  to  do  with  their  own 
maintenance,  we  have  still  clearer  proof  that  the  individual- 
ities of  the  members  are  partially  merged  in  the  individuality 
of  the  group.  Other  organisms  belonging  to  the  same  order, 
display  still  more  decidedly  this  transition  from  simple  indi- 
vidualities to  a  complex  individuality.  In  the  Diphyes  there 


INDIVIDUALITY.  247 

is  a  special  modification  of  one  or  more  members  of  the  poly- 
pedom  into  a  swimming  apparatus  which,  by  its  rhythmical 
contractions,  propels  itself  through  the  water,  drawing  the 
polypedom  after  it.  And  in  the  more  differentiated  Physalia 
various  organs  result  from  the  metamorphosis  of  parts 
which  are  the  homologues  of  individual  polypes.  In  this 
last  instance,  the  individuality  of  the  aggregate  is  so  pre- 
dominant that  the  individualities  of  its  members  are  practi- 
cally lost.  This  combination  of  individualities  in  such 
way  as-  to  produce  a  composite  individual,  meets  us  in  other 
forms  among  the  ascidians.  While  in  some  of  these,  as  in 
the  Clavelina  and  in  the  Botryllidce,  the  animals  associated 
are  but  little  subordinated  to  the  community  they  form,  in 
others  they  are  so  combined  as  to  form  a  compound  indi- 
vidual. The  pelagic  ascidian  Doliolum  is  an  example.  "  Here 
we  find  a  large  individual  which  swims  by  contractions  of 
circular  muscular  bands,  carries  a  train  of  smaller  individuals 
attached  to  a  long  dorsal  process  of  the  test.  These  are 
arranged  in  three  rows :  those  constituting  the  lateral  row 
have  wide  mouths  and  no  sexual  organs  or  organs  of  locomo- 
tion— they  subserve  the  nutrition  of  the  colony,  a  truth 
which  is  illustrated  by  the  fact  that  as  soon  as  they  are 
properly  developed  the  large  individual  (the  mother)  loses 
her  alimentary  canal ; "  while  from  the  median  row  are 
eventually  derived  the  sexual  zoids. 

On  the  hypothesis  of  Evolution,  perplexities  of  this  nature 
are  just  such  as  we  might  anticipate.  If  Life  in  general 
commenced  with  minute  and  simple  forms,  like  those  out  of 
which  all  organisms,  however  complex,  now  originate;  and 
if  the  transitions  from  these  primordial  units  to  organisms 
made  up  of  groups  of  such  units,  and  to  higher  organisms 
made  up  of  groups  of  such  groups  took  place  by  degrees;  it 
is  clear  that  individualities  of  the  first  and  simplest  order 
would  merge  gradually  in  those  of  a  larger  and  more  com- 
plex order,  and  these  again  in  others  of  an  order  having  still 


248  THE  INDUCTIONS  OP  BIOLOGY. 

greater  bulk  and  organization.  Hence  it  would  be  impossible 
to  say  where  the  lower  individualities  ceased  and  the  higher 
individualities  commenced. 

§  73.  To  meet  these  difficulties,  it  has  been  proposed  that 
the  whole  product  of  a  single  fertilized  germ  shall  be  re- 
garded as  a  single  individual;  whether  such  whole  product 
be  organized  into  one  mass,  or  whether  it  be  organized  into 
many  masses  that  are  partially  or  completely  separate.  It 
is  urged  that  whether  the  development  of  the  fertilized  germ 
be  continuous  or  discontinuous  (§50)  is  a  matter  of  secondary 
importance;  that  the  totality  of  living  tissue  to  which  the 
fertilized  germ  gives  rise  in  any  one  case,  is  the  equivalent  of 
the  totality  to  which  it  gives  rise  in  any  other  case ;  and  that 
we  must  recognize  this  equivalence,  whether  such  totality 
of  living  tissue  takes  a  concrete  or  a  discrete  arrangement. 
In  pursuance  of  this  view,  a  zoological  individual  is  consti- 
tuted either  by  any  such  single  animal  as  a  mammal  or  bird, 
which  may  properly  claim  the  title  of  a  zoon,  or  by  any  such 
group  of  animals  as  the  numerous  Medusce  that  have  been 
developed  from  the  same  egg,  which  are  to  be  severally  dis- 
tinguished as  zooids. 

Admitting  it  to  be  very  desirable  that  there  should  be 
words  for  expressing  these  relations  and  this  equivalence,  it 
may  be  objected  that  to  apply  the  word  individual  to  a  num- 
ber of  separate  living  bodies,  is  inconvenient :  conflicting  so 
much,  as  it  does,  with  the  ordinary  conception  which  this  word 
suggests.  It  seems  a  questionable  use  of  language  to  say  that 
the  countless  masses  of  Anacharis  Alsinastrum  (now  Eloidca 
canadcnsis)  which,  within  these  few  years,  have  grpwn  up  in 
our  rivers,  canals,  and  ponds,  are  all  parts  of  one  individual : 
and  yet  as  this  plant  does  not  seed  in  England,  these  count- 
less masses^  having  arisen  by  discontinuous  development, 
must  be  so  regarded  if  we  accept  the  above  definition. 

It  may  be  contended,  too,  that  while  it  does  violence  to 
our  established  way  of  thinking,  this  mode  of  interpreting 


INDIVIDUALITY.  249 

the  facts  is  not  without  its  difficulties.  Something  seems  to 
be  gained  by  restricting  the  application  of  the  title  indi- 
vidual, to  organisms  which,  being  in  all  respects  fully  devei- 
opedj  possess  the  power  of  producing  their  kind  after  the 
ordinary  sexual  method,  and  denying  this  title  to  those  in- 
complete organisms  which  have  not  this  power.  But  the 
definition  does  not  really  establish  this  distinction  for  us.  On 
the  one  hand,  we  have  cases  in  which,  as  in  the  working  bee, 
the  whole  of  the  germ-product  is  aggregated  into  a  single 
organism;  and  yet,  though  an  individual  according  to  the 
definition,  this  organism  has  no  power  of  reproducing  its 
kind.  On  the  other  hand,  we  have  cases  like  that  of  the 
perfect  Aphis,  where  the  organism  is  but  an  infinitesimal 
part  of  the  germ  product,  and  yet  has  that  completeness 
required  for  sexual  reproduction.  Further,  it  might 

be  urged  with  some  show  of  reason,  that  if  the  conception  of 
individuality  involves  the  conception  of  completeness,  then, 
an  organism  which  possesses  an  independent  power  of  repro- 
ducing itself,  being  more  complete  than  an  organism  in  which 
this  power  is  dependent  on  the  aid  of  another  organism,  is 
more  individual. 

§  74.  There  is,  indeed,  as  already  implied,  no  definition 
of  individuality  that  is  unobjectionable.  All  we  can  do  is  to 
make  the  best  practicable  compromise. 

As  applied  either  to  an  animate  or  an  inanimate  object, 
the  word  individual  ordinarily  connotes  union  among  the 
parts  of  the  object  and  separateness  from  other  objects.  This 
fundamental  element  in  the  conception  of  individuality,  we 
cannot  with  propriety  ignore  in  the  biological  application 
of  the  word.  That  which  we  call  an  individual  plant  or 
animal  must,  therefore,  be  some  concrete  whole  and  not  a 
discrete  whole.  If,  however,  we  say  that  each  concrete 

living  whole  is  to  be  regarded  as  an  individual,  we  are  still 
met  by  the  question — What  constitutes  a  concrete  living 
whole?  A  young  organism  arising  by  internal  or  external 


HO  TtlK  WntfrriONS  OP 

gemmation  from  a  parent  organism,  passes  gradually  from  a 
>uh-  in  whieh  it  is  an  indistinguishable  part  of  the  parent 
organism  to  a  state  in  which  it  is  a  separate  organism  of  like 
structure  with  the  parent  At  what  stage  does  it  become  an 
individual  ?  And  if  its  individuality  be  conceded  only  when 
it  completely  separates  from  the  parent,  must  we  deny  indi- 
viduality to  all  organisms  thus  produced  which  permanently 
retain  their  connexions  with  their  parents?  Or  again,  what 
must  we  say  of  the  Hwtwotglw*  which  is  an  arm  of  the 
Cuttle-fish  that  undergoes  a  special  development  and  then, 
detaching:  itself*  lives  independently  for  a  considerable 
period  ?  And  what  must  we  say  of  the  larval  nemertine  worm 
the  pilidium  of  which  with  its  nervous  system  is  left  to  move 
about  awhile  after  the  developing  worm  has  dropped  out 
of  it* 

To  answer  such  questions  we  must  revert  to  the  definition 
of  Life.  The  distinction  between  individual  in  its  biological 
sense,  and  individual  in  its  more  general  sense,  must  consist 
in  the  manifestation  of  Life,  properly  so  called.  Life  we 
have  seen  to  be,  **  the  definite  combination  of  heterogeneous 
changes,  both  simultaneous  and  successive,  in  correspondence 
with  external  co-existences  and  sequences,**  Hence,  a  bio- 
logical individual  is  any  concrete  whole  having  a  structure 
which  enables  it,  when  placed  in  appropriate  conditions,  to 
continuously  adjust  its  internal  relations  to  external  relations, 
so*  as  to  maintain  the  equilibrium  of  its  functions.  In 

pursuance  of  this  conception,  we  must  consider  as  individuals 
all  those  wholly  or  partially  independent  organised  masses 
which  arise  by  multicentral  and  nmltiaxial  development  that 
is  either  continuous  or  discontinuous  ( §  50) .  We  must  accord 
the  title  to  each  separate  aphis,  each  polype  of  a  polypedom, 
each  bud  or  shoot  of  a  flowering  plant,  whether  it  detaches 
itself  as  a  bulbil  or  remains  attached  as  a  branch. 

By  thus  interpreting  the  facts  we  do  not,  indeed,  avoid  all 
anomalies.  While,  among  flowering  plants,  the  power  of 
infepotdent  growth  and  development  is  usually  possessed 


INDIVIDUALITY.  251 

only  by  shoots  or  axes ;  yet,  in  some  cases,  as  in  that  of  the 
Begonia-leaf  awhile  since  mentioned,  the  appendage  of  an 
axis,  or  even  a  small  fragment  of  such  appendage,  is  capable 
of  initiating  and  carrying  on  the  functions  of  life;  and  in 
other  cases,  as  shown  by  M.  Naudin  in  the  Drosera  inter- 
media, young  plants  are  occasionally  developed  from  the  sur- 
faces of  leaves.  Nor  among  forms  like  the  compound 
Hydrozoa,  does  the  definition  enable  us  to  decide  where  the 
line  is  to  be  drawn  between  the  individuality  of  the  group 
and  the  individualities  of  the  members :  merging  into  each 
other,  as  these  do,  in  different  degrees.  But,  as  before  said, 
such  difficulties  must  necessarily  present  themselves  if  organic 
forms  have  arisen  by  insensible  gradations.  We  must  be 
content  with  a  course  which  commits  us  to  the  smallest 
number  of  incongruities;  and  this  course  is,  to  consider  as 
an  individual  any  organized  mass  which  is  capable  of  inde- 
pendently'carrying  on  that  continuous  adjustment  of  inner  to 
outer  relations  which  constitutes  Life. 


CHAPTER  VIA. 

CELL-LIFE    AND    CELL-MULTIPLICATION. 

§  74a.  THE  progress  of  science  is  simultaneously  towards 
simplification  and  towards  complication.  Analysis  simplifies 
its  conceptions  by  resolving  phenomena  into  their  factors, 
and  by  then  showing  how  each  simple  mode  of  action  may 
be  traced  under  multitudinous  forms ;  while,  at .  the  same 
time,  synthesis  shows  how  each  factor,  by  cooperation  with 
various  other  factors  in  countless  modes  and  degrees,  pro- 
duces different  results  innumerable  in  their  amounts  and 
varieties.  Of  course  this  truth  holds  alike  of  processes  and 
of  products.  Observation  and  the  grouping  into  classes  make 
it  clear  that  through  multitudinous  things  superficially  un- 
like there  run  the  same  cardinal  traits  of  structure;  while, 
along  with  these  major  unities,  examination  discloses  innu- 
merable minor  diversities. 

A  concomitant  truth,  or  the  same  truth  under  another 
aspect,  is  that  Nature  everywhere  presents  us  with  complexi- 
ties within  complexities,  which  go  on  revealing  themselves  as 
we  investigate  smaller  and  smaller  objects.  In  a  preceding 
chapter  (§§  54a,  546)  it  was  pointed  out  that  each  primitive 
organism,  in  common  with  each  of  the  units  out  of  which 
the  higher  and  larger  organisms  are  built,  was  found  a  gene- 
ration ago  to  consist  of  nucleus,  protoplasm,  and  cell-wall. 
This  general  conception  of  a  cell  remained  for  a  time  the 
outcome  of  inquiry;  but  with  the  advance  of  microscopy  it 


CELL-LIFE  AND  CELL-MULTIPLICATION.  253 

became  manifest  that  within  these  minute  structures  pro- 
cesses and  products  of  an  astonishing  nature  are  to  be  seen. 
These  we  have  now  to  contemplate. 

In  the  passages  just  referred  to  it  was  said  that  the  ex- 
ternal layer  or  cell-wall  is  a  non-essential,  inanimate  part  pro- 
duced by  the  animate  contents.  Itself  a  product  of  proto- 
plasmic action,  it  takes  no  part  in  protoplasmic  changes,  and 
may  therefore  here  be  ignored. 

§  74&.  One  of  the  complexities  within  complexities  was 
disclosed  when  it  was  found  that  the  protoplasm  itself  has  a 
complicated  structure.  Different  observers  have  described  it 
as  constituted  by  a  network  or  reticulum,  a  sponge-work,  a 
foam-work.  Of  these  the  first  may  be  rejected;  since  it 
implies  a  structure  lying  in  one  plane.  If  we  accept  the 
second  we  have  to  conceive  the  threads  of  protoplasm,  corre- 
sponding to  the  fibres  of  the  sponge,  as  leaving  interstices 
filled  either  with  liquid  or  solid.  They  cannot  be  filled  with 
a  continuous  solid,  since  all  motion  of  the  protoplasm  would 
be  negatived;  and  that  their  content  is  not  liquid  seems 
shown  by  the  fact  that  its  parts  move  about  under  the  form 
of  granules  or  microsomes.  But  the  conception  of  moving 
granules  implies  the  conception  of  immersion  in  a  liquid  or 
semi-liquid  substance  in  which  they  move — not  a  sponge- 
work  of  threads  but  a  foam-work,  consisting  everywhere  of 
septa  interposed  among  the  granules.  This  is  the  hypothesis 
which  sundry  microscopists  espouse,  and  which  seems  me- 
chanically the  most  feasible:  the  only  one  which  consists 
with  the  "  streaming  "  of  protoplasm.  Ordinarily  the  name 
protoplasm  is  applied  to  the  aggregate  mass — the  semi-liquid, 
hyaline  substance  and  the  granules  or  microsomes  it  con- 
tains. 

What  these  granules  or  microsomes  are — whether,  as  some 
have  contended,  they  are  the  essential  living  elements  of  the 
protoplasm,  or  whether,  as  is  otherwise  held,  they  are  nutri- 
tive particles,  is  at  present  undecided.  But  the  fact,  alleged 


254  THE  INDUCTIONS  OF  BIOLOGY. 

by  sundry  observers,  that  the  microsomes  often  form  rows, 
held  together  by  intervening  substance,  seems  to  imply  that 
these  minute  bodies  are  not  inert.  Leaving  aside  unsettled 
questions,  however,  one  fact  of  significance  is  manifest — an 
immense  multiplication  of  surfaces  over  which  inter-action 
may  take  place.  Anyone  who  drops  .into  dilute  sulphuric 
acid  a  small  nail  and  then  drops  a  pinch  of  iron  filings,  will 
be  shown,  by  the  rapid  disappearance  of  the  last  and  the  long 
continuance  of  the  first,  how  greatly  the  increasing  of  sur- 
faces by  multiplication  of  fragments  facilitates  change.  The 
effect  of  subdivision  in  producing  a  large  area  in  a  small 
space,  is  shown  in  the  lungs,  where  the  air-cells  on  the  sides 
of  which  the  blood-vessels  ramify,  are  less  than  1/iOOth  of 
an  inch  in  diameter,  while  they  number  700,000,000.  In 
the  composition  of  every  tissue  we  see  the  same  principle. 
The  living  part,  or  protoplasm,  is  divided  into  innumerable 
protoplasts,  among  which  are  distributed  the  materials  and 
agencies  producing  changes.  And  now  we  find  this  principle 
carried  still  deeper  in  the  structure  of  the  protoplasm  itself. 
Each  microscopic  portion  of  it  is  minutely  divided  in  such 
ways  that  its  threads  or  septa  have  multitudinous  contacts 
with  those  included  portions  of  matter  which  take  part  in  its 
activities. 

Concerning  the  protoplasm  contained  in  each  cell,  named 
by  some  cytoplasm,  it  remains  to  say  that  it  always  includes  a 
small  body  called  the  centrosome,  which  appears  to  have  a 
directive  function.  Usually  the  centrosome  lies  outside  the 
nucleus,  but  is  alleged  to  be  sometimes  within  it.  During 
what  is  called  the  "  resting  stage,"  or  what  might  more  pro- 
perly be  called  the  growing  stage  (for  clearly  the  occasional 
divisions  imply  that  in  the  intervals  between  them  there  has 
been  increase)  the  centrosome  remains  quiescent,  save  in  the 
respect  that  it  exercises  some  coercive  influence  on  the  pro- 
toplasm around.  This  results  in  the  radially-arranged  lines 
constituting  an  "  aster."  What  is  the  nature  of  the  coercion 
exercised  by  the  centrpsoine— a  body  hardly  distinguishable 


CELL-LIFE  AND  CELL-MULTIPLICATION.  255 

in  size  from  the  microsomes  or  granules  of  protoplasm  around 
— is  not  known.  It  can  scarcely  be  a  repelling  force;  since, 
in  a  substance  of  liquid  or  semi-liquid  kind,  this  could  not 
produce  approximately  straight  lines.  That  it  is  an  attrac- 
tive force  seems  more  probable ;  and  the  nature  of  the  attrac- 
tion would  be  comprehensible  did  the  centrosome  augment 
in  bulk  with  rapidity.  For  if  integration  were  in  progress, 
the  drawing  in  of  materials  might  well  produce  converging 
lines.  But  this  seems  scarcely  a  tenable  interpretation ;  since, 
during  the  so-called  "  resting  stage,"  this  star-like  structure 
exists — exists,  that  is,  while  no  active  growth  of  the  centro- 
some is  going  on. 

Eespecting  this  small  body  we  have  further  to  note  that, 
like  the  cell  as  a  whole,  it  multiplies  by  fission,  and  that  the 
bisection  of  it  terminates  the  resting  or  growing  stage  and 
initiates  those  complicated  processes  by  which  two  cells  are 
produced  out  of  one:  the  first  step  following  the  fission 
being  the  movement  of  the  halves,  with  their  respective  com- 
pleted asters,  to  the  opposite  sides  of  the  nucleus. 

§  74c.  With  the  hypothesis,  now  general,  that  the  nucleus 
or  kernel  of  a  cell  is  its  essential  part,  there  has  not  an- 
naturally  grown  up  the  dogma  that  it  is  always  present; 
but  there  is  reason  to  think  that  the  evidence  is  somewhat 
strained  to  justify  this  dogma. 

In  the  first  place,  beyond  the  cases  in  which  the  nucleus, 
though  ordinarily  invisible,  is  said  to  have  been  rendered 
visible  by  a  re-agent,  there  are  cases,  as  in  the  already-named 
Archerina,  where  no  re-agent  makes  one  visible.  In  the 
second  place,  there  is  the  admitted  fact  that  some  nuclei  are 
diffused;  as  in  Trachelocerca  and  some  other  Infusoria.  In 
them  the  numerous  scattered  granules  are  supposed  to  con- 
stitute a  nucleus :  an  interpretation  obviously  biassed  by  the 
desire  to  save  the  generalization.  In  the  third  place,  the 
nucleus  is  frequently  multiple  in  cells  of  low  types;  as  in 
some  families  of  Algae  and  predominantly  among  Fungi. 


256  THE  INDUCTIONS  OF  BIOLOGY. 

Once  more,  the  so-called  nucleus  is  occasionally  a  branching 
structure  scarcely  to  be  called  a  "  kernel." 

The  facts  as  thus  grouped  suggest  that  the  nucleus  has 
arisen  in  conformity  with  the  law  of  evolution — that  the 
primitive  protoplast,  though  not  homogeneous  in  the  full 
sense,  was  homogeneous  in  the  sense  of  being  a  uniformly 
granular  protoplasm;  and  that  the  protoplasts  with  diffused 
nuclei,  together  with  those  which  are  multi-nucleate,  and 
those  which  have  nuclei  of  a  branching  form,  represent  stages 
in  that  process  by  which  the  relatively  homogeneous  proto- 
plast passed  into  the  relatively  heterogeneous  one  now  almost 
universal. 

Concerning  the  structure  and  composition  of  the  developed 
nucleus,  the  primary  fact  to  be  named  is  that,  like  the  sur- 
rounding granular  cytoplasm,  it  is  formed  of  two  distinct 
elements.  It  has  a  groundwork  or  matrix  not  differing  much 
from  that  of  the  cytoplasm,  and  at  some  periods  continuous 
with  it;  and  immersed  in  this  it  has  a  special  matter  named 
chromatin,  distinguished  from  its  matrix  by  becoming  dyed 
more  or  less  deeply  when  exposed  to  fit  re-agents.  During 
the  "  resting  stage,"  or  period  of  growth  and  activity  which 
coTnes  between  periods  of  division,  the  chromatin  is  dispersed 
throughout  the  ground-substance,  either  in  discrete  portions 
or  in  such  way  as  to  form  an  irregular  network  or  sponge- 
work,  various  in  appearance.  When  the  time  for  fission  is 
approaching  .this  dispersed  chromatin  begins  to  gather  itself 
together :  reaching  its  eventual  concentration  through  several 
stages.  By  its  concentration  are  produced  the  chromosomes, 
constant  in  number  in  each  species  of  plant  or  animal.  It 
is  alleged  that  the  substance  of  the  chromosomes  is  not 
continuous,  but  consists  of  separate  elements  or  granules, 
which  have  been  named  chromomeres;  and  it  is  also  alleged 
that,  whether  in  the  dispersed  or  integrated  form,  each  chro- 
mosome retains  its  individuality — that  the  chromomeres 
composing  it,  now  spreading  out  into  a  network  and  now 
uniting  into  a  worm-like  body,  form  a  group  which  never 


CELL-LIFE  AND  CELL-MULTIPLICATION.          25T 

loses  its  identity.  Be  this  as  it  may,  however,  the  essential 
fact  is  that  during  the  growth-period  the  chromatin  sub- 
stance is  widely  distributed,  and  concentration  of  it  is  one  of 
the  chief  steps  towards  a  division  of  the  nucleus  and  pre- 
sently of  the  cell. 

During  this  process  of  mitosis  or  karyokinesis,  the  dis- 
persed chromatin  having  passed  through  the  coil-stage, 
reaches  presently  the  star-stage,  in  which  the  chromosomes 
are  arranged  symmetrically  about  the  equatorial  plane  of  the 
nucleus.  Meanwhile  in  each  of  them  there  has  been  a  pre- 
paration for  splitting  longitudinally  in  such  way  that  the 
halves  when  separated  contain  (or  are  assumed  to  contain) 
equal  numbers  of  the  granules  or  chromomeres,  which  some 
think  are  the  ultimate  morphological  units  of  the  chromo- 
somes. A  simultaneous  change  has  occurred :  there  has  been 
in  course  of  formation  a  structure  known  as  the  amphiaster. 
The  two  centrosomes  which,  as  before  said,  place  themselves 
on  opposite  sides  of  the  nucleus,  become  the  terminal  poles 
of  a  spindle-shaped  arrangement  of  fibres,  arising  mainly 
from  the  groundwork  of  the  nucleus,  now  continuous  with 
the  groundwork  of  the  cytoplasm.  A  conception  of  this 
structure  may  be  formed  by  supposing  that  the  radiating 
fibres  of  the  respective  asters,  meeting  one  another  and 
uniting  in  the  intermediate  space,  thereafter  exercise  a  trac- 
tive force;  since  it  is  clear  that,  while  the  central  fibres  of 
the  bundle  will  form  straight  lines,  the  outer  ones,  pulling 
against  one  another  not  in  straight  lines,  will  form  curved 
lines,  becoming  more  pronounced  in  their  curvatures  as  the 
distance  from  the  axis  increases.  That  a  tractive  force  is  at 
work  seems  inferable  from  the  results.  For  the  separated 
halves  of  the  split  chromosomes,  which  now  form  clusters  on 
the  two  sides  of  the  equatorial  plane,  gradually  part  com- 
pany, and  are  apparently  drawn  as  clusters  towards  the  op- 
posing centrosomes.  As  this  change  progresses  the  original 
nucleus  loses  its  individuality.  The  new  chromosomes, 
halves  of  the  previous  chromosomes,  concentrate  to  found 


258  THE  INDUCTIONS  OP  BIOLOGY.     , 

two  new  nuclei;  and,  by  something  like  a  reversal  of  the 
stages  above  described,  the  chromatin  becomes  dispersed 
throughout  the  substance  of  each  new  nucleus.  While  this 
is  going  on  the  cell  itself,  undergoing  constriction  round  its 
equator,  divides  into  two. 

Many  parts  of  this  complex  process  are  still  imperfectly 
understood,  and  various  opinions  concerning  them  are  cur- 
rent. But  the  essential  facts  are  that  this  peculiar  sub- 
stance, the  chromatin,  at  other  times  existing  dispersed,  is, 
when  division  is  approaching,  gathered  together  and  dealt 
with  in  such  manner  as  apparently  to  insure  equal  quantities 
being  bequeathed  by  the  mother-cell  to  the  two  daughter- 
cells. 

§  74d.  What  is  the  physiological  interpretation  of  these 
structures  and  changes?  What  function  does  the  nucleus 
discharge;  and,  more  especially,  what  is  the  function  dis- 
charged by  the  chromatin?  There  have  been  to  these  ques- 
tions sundry  speculative  answers. 

The  theory  espoused  by  some,  that  the  nucleus  is  the 
regulative  organ  of  the  cell,  is  met  by  difficulties.  One  of 
them  is  that,  as  pointed  out  in  the  chapter  on  "  Structure," 
the  nucleus,  though  morphologically  central,  is  not  central 
geometrically  considered;  and  that  its  position,  often  near  to 
some  parts  of  the  periphery  and  remote  from  others,  almost 
of  itself  negatives  the  conclusion  that  its  function  is  directive 
in  the  ordinary  sense  of  the  word.  It  could  not  well  control 
the  cytoplasm  in  the  same  ways  in  all  directions  and  at 
different  distances.  A  further  difficulty  is  that  the  cyto- 
plasm when  deprived  of  its  nucleus  can  perform  for  some 
time  various  of  its  actions,  though  it  eventually  dies  without 
reproducing  itself. 

For  the  hypothesis  that  the  nucleus  is  a  vehicle  for  trans- 
mitting hereditary  characters,  the  evidence  seems  strong. 
When  it  was  shown  that  the  head  of  a  spermatozoon  is 
simply  a  detached  nucleus,  and  that  its  fusion  with  the 


CELL-LIFE  AND  CELL-MULTIPLICATION.  259 

nucleus  of  an  ovum  is  the  essential  process  initiating  the 
development  of  a  new  organism,  the  legitimate  inference 
appeared  to  be  that  these  two  nuclei  convey  respectively  the 
paternal  and  maternal  traits  which  are  mingled  in  the  off- 
spring. And  when  there  came  to  be  discerned  the  karyoki- 
nesis  by  which  the  chromatin  is,  during  cell-fission,  exactly 
halved  between  the  nuclei  of  the  daughter-cells,  the  conclu- 
sion was  drawn  that  the  chromatin  is  more  especially  the 
agent  of  inheritance.  But  though,  taken  by  themselves,  the 
phenomena  of  fertilization  seem  to  warrant  this  inference, 
the  inference  does  not  seem  congruous  with  the  phenomena 
of  ordinary  cell-multiplication — phenomena  which  have  noth- 
ing to  do  with  fertilization  and  the  transmission  of  here- 
ditary characters.  No  explanation  is  yielded  of  the  fact  that 
ordinary  cell-multiplication  exhioits  an  elaborate  process  for 
exact  halving  of  the  chromatin.  Why  should  this  substance 
be' so  carefully  portioned  out  among  the  cells  of  tissues  which 
are  not  even  remotely  concerned  with  propagation  of  the 
species?  If  it  be  said  that  the  end  achieved  is  the  convey- 
ance of  paternal  and  maternal  qualities  in  equal  degrees 
to  every  tissue;  then  the  reply  is  that  they  do  not  seem  to 
be  conveyed  in  equal  degrees.  In  the  offspring  there  is  not 
a  uniform  diffusion  of  the  two  sets  of  traits  throughout  all 
parts,  but  an  irregular  mixture  of  traits  of  the  one  with  traits 
of  the  other. 

In  presence  of  these  two  suggested  hypotheses  and  these 
respective  difficulties,  may  we  not  suspect  that  the  action  of 
the  chromatin  is  one  which  in  a  way  fulfils  both  functions? 
Let  us  consider  what  action  may  do  this. 

§  7-ie.  The  chemical  composition  of  chromatin  is  highly 
complex,  and  its  complexity,  apart  from  other  traits,  implies 
relative  instability.  This  is  further  implied  by  the  special 
natures  of  its  components.  Various  analyses  have  shown 
that  it  consists  of  an  organic  acid  (which  has  been  called 
nucleic  acid)  rich  in  phosphorus,  combined  with  an  albu- 


260  THE  INDUCTIONS  OF  BIOLOGY. 

minous  substance :  probably  a  combination  of  various  pro- 
teids.  And  the  evidence,  as  summarised  by  Wilson,  seems 
to  show  that  where  the  proportion  of  phosphorized  acid  is 
high  the  activity  of  the  substance  is  great,  as  in  the  heads  of 
spermatozoa;  while,  conversely,  where  the  quantity  of  phos- 
phorus is  relatively  small,  the  substance  approximates  in 
character  to  the  cytoplasm.  Now  (like  sulphur,  present  in 
the  albuminoid  base),  phosphorus  is  an  element  which, 
besides  having  several  allotropic  forms,  has  a  great  affinity 
for  oxygen;  and  an  organic  compound  into  which  it  enters, 
beyond  the  instability  otherwise  caused,  has  a  special  insta- 
bility caused  by  its  presence.  The  tendency  to  undergo 
change  will  therefore  be  great  when  the  proportion  of  the 
phosphorized  component  is  great.  Hence  the  statement  that 
"  the  chemical  differences  between  chromatin  and  cytoplasm, 
striking  and  constant  as  they  are,  are  differences  of  degree 
only; "  and  the  conclusion  that  the  activity  of  the  chromatin 
is  specially  associated  with  the  phosphorus.* 

What,  now,  are  the  implications?  Molecular  agitation 
results  from  decompositon  of  each  phosphorized  molecule: 
shocks  are  continually  propagated  around.  From  the  chro- 
matin, units  of  which  are  thus  ever  falling  into  stabler  states, 
there  are  ever  being  diffused  waves  of  molecular  motion, 
setting  up  molecular  changes  in  the  cytoplasm.  The  chro- 
matin stands  towards  the  other  contents  of  the  cell  in  the 
same  relation  that  a  nerve-element  stands  to  any  element  of 

*  While  the  proof  was  in  my  hands  there  was  published  in  Sdence  Pro- 
gress an  essay  by  Dr.  T.  G.  Brodie  on  "  The  Phosphorus-containing  Substances 
of  the  Cell."  In  this  essay  it  is  pointed  out  that  '•  nucleic  acid  is  particu- 
larly characterized  by  its  instability  ...  In  the  process  of  purification  it  is 
extremely  liable  to  decompose,  with  the  result  that  it  loses  a  considerable  part 
of  its  phosphorus.  In  the  second  place  it  is  most  easily  split  up  in  another 
manner  in  which  it  loses  a  considerable  part  of  its  nitrogen  ...  To  avoid  the 
latter  source  of  error  he  [Miescher]  found  that  it  was  necessary  to  keep  the 
temperature  of  all  solutions  down  to  0°  C.,  the  whole  time  of  the  preparation." 
These  facts  tend  strongly  to  verify  the  hypothesis  that  the  nucleus  is  a  source 
of  perpetual  molecular  disturbance — not  a  regulating  centre  but  a  stimulating 
centre. 


CELL-LIFE  AND  CELL-MULTIPLICATION.  261 

an  organism  which  it  excites:  an  interpretation  congruous 
with  the  fact  that  the  chromatin  is  as  near  to  as,  and  indeed 
nearer  than,  a  nerve-ending  to  any  minute  structure  stimu- 
lated by  it. 

Several  confirmatory  facts  may  be  named.  During  the 
intervals  between  cell-fissions,  when  growth  and  the  usual 
cell-activities  are  being  carried  on,  the  chromatin  is  dispersed 
throughout  the  nucleus  into  an  irregular  network:  thus 
greatly  increasing  the  surface  of  contact  between  its  sub- 
stance and  the  substances  in  which  it  is  imbedded.  As  has 
been  remarked,  this  wide  distribution  furthers  metabolism — 
a  metabolism  which  in  this  case  has,  as  we  infer,  the  func- 
tion of  generating,  not  special  matters  but  special  motions. 
Moreover,  just  as  the  wave  of  disturbance  a  nerve  carries 
produces  an  effect  which  is  determined,  not  by  anything 
which  is  peculiar  in  itself,  but  by  the  peculiar  nature  of  the 
organ  to  which  it  is  carried — muscular,  glandular  or  other; 
so  here,  the  waves  diffused  from  the  chromatin  do  not  de- 
termine the  kinds  of  changes  in  the  cytoplasm,  but  simply 
excite  it:  its  particular  activities,  whether  of  movement, 
absorption,  or  structural  excretion,  being  determined  by  its 
constitution.  And  then,  further,  we  observe  a  parallelism 
between  the  metabolic  changes  in  the  two  cases;  for,  on  the 
one  hand,  "diminished  staining  capacity  of  the  chromatin 
[implying  a  decreased  amount  of  phosphorus,  which  gives 
the  staining  capacity]  occurs  during  a  period  of  intense  con- 
structive activity  in  the  cytoplasm ;  "  and,  on  the  other  hand, 
in  high  organisms  having  nervous  systems,  the  intensity  of 
nervous  action  is  measured  by  the  excretion  of  phosphates — 
by  the  using  up  of  the  phosphorus  contained  in  nerve-cells. 

For  thus  interpreting  the  respective  functions  of  chro- 
matin and  cytoplasm,  yet  a  further  reason  may  be  given. 
One  of  the  earliest  general  steps  in  the  evolution  of  the 
Metazoa,  is  the  differentiation  of  parts  which  act  from  parts 
which  make  them  act.  The  Hydrozoa  show  us  this.  In  the 
hydroid  stage  there  are  no  specialized  contractile  organs: 
18 


2G2  THE  INDUCTIONS  OF   BIOLOGY. 

these  are  but  incipient:  individual  ectoderm  cells  have  mus- 
cular processes.  Nor  is  there  any  "  special  aggregation  of 
nerve-cells."  If  any  stimulating  units  exist  they  are 
scattered.  But  in  the  Medusa-stage  nerve-matter  is  collected 
into  a  ring  round  the  edge  of  the  umbrella.  That  is  to  say, 
in  the  undeveloped  form  such  motor  action  as  occurs  is  not 
effected  by  a  specialized  part  which  excites  another  part; 
but  in  the  developed  form  a  differentiation  of  the  two  has 
taken  place.  All  higher  types  exhibit  this  differentia- 
tion. Be  it  muscle  or  gland  or  other  operating  organ,  the 
cause  of  its  activity  lies  not  in  itself  but  in  a  nervous  agent, 
local  or  central,  with  which  it  is  connected.  Hence, 
then,  there  is  congruity  between  the  above  interpretation 
and  certain  general  truths  displayed  by  animal  organization 
at  large.  We  may  infer  that  in  a  way  parallel  to  that  just 
indicated,  cell-evolution  was,  under  one  of  its  aspects,  a 
change  from  a  stage  in  which  the  exciting  substance  and  the 
substance  excited  were  mingled  with  approximate  uniformity, 
to  a  stage  in  which  the  exciting  substance  was  gathered 
together  into  the  nucleus  and  finally  into  the  chromosomes: 
leaving  behind  the  substance  excited,  now  distinguished  as 
cytoplasm. 

§  74/.  Some  further  general  aspects  of  the  phenomena 
appear  to  be  in  harmony  with  this  interpretation.  Let  us 
glance  at  them. 

In  Chapters  III  and  IIlA  of  the  First  Part,  reasons  were 
given  for  concluding  that  in  the  animal  organism  nitroge- 
nous substances  play  the  part  of  decomposing  agents  to  the 
carbo-hydrates — that  the  molecular  disturbance  set  up  by 
the  collapse  of  a  proteid  molecule  destroys  the  equilibrium 
of  sundry  adjacent  carbo-hydrate  molecules,  and  causes  that 
evolution  of  energy  which  accompanies  their  fall  into  mole- 
cules of  simpler  compounds.  Here,  if  the  foregoing  argu- 
ment is  valid,  we  may  conclude  that  this  highly  complex 
phosphorized  compound  which  chromatin  contains,  plays  the 


CELL-LIFE  AND  CELL-MULTIPLICATION.  263 

same  part  to  the  adjacent  nitrogenous  compounds  as  these 
play  to  the  carbo-hydrates.  If  so,  we  see  arising  a  stage 
earlier  that  "  general  physiological  method "  illustrated  in 
§  23f.  It  was  there  pointed  out  that  in  animal  organisms 
the  various  structures  are  so  arranged  that  evolution  of  a 
small  amount  of  energy  in  one,  sets  up  evolution  of  a  larger 
amount  of  energy  in  another;  and  often  this  multiplied 
energy  undergoes  a  second  multiplication  of  like  kind.  If 
this  view  is  tenable,  we  may  now  suspect  that  this  method 
displayed  in  the  structures  of  the  Metazoa  was  initiated  in 
the  structures  of  the  Protozoa,  and  consequently  characterizes 
those  homologues  of  them  which  compose  the  Metazoa. 

When  contemplated  from  the  suggested  point  of  view, 
karyokinesis  appears  to  be  not  wholly  incomprehensible. 
For  if  the  chromatin  yields  the  energy  which  initiates 
changes  throughout  the  rest  of  the  cell,  we  may  see  why 
there  eventually  arises  a  process  for  exact  halving  of  the 
chromatin  in  a  mother-cell  between  two  daughter-cells.  To 
make  clear  the  reason,  let  us  suppose  the  portioning  out  of 
the  chromatin  leaves  one  of  the  two  with  a  sensibly  smaller 
amount  than  the  other.  What  must  result?  Its  source  of 
activity  being  relatively  less,  its  rate  of  growth  and  its 
energy  of  action  will  be  less.  If  a  protozoon,  the  weaker 
progeny  arising  by  division  of  it  will  originate  an  inferior 
stirp,  unable  to  compete  successfully  with  that  arising  from 
the  sister-cell  endowed  with  a  larger  portion  of  chromatin.  By 
continual  elimination  of  the  varieties  which  produce  unequal 
halving,  necessarily  at  a  disadvantage  if  a  moiety  of  their 
members  tend  continually  to  disappear,  there  will  be  estab- 
lished a  variety  in  which  the  halving  is  exact :  the  character 
of  this  variety  being  such  that  all  its  members  aid  the  per- 
manent multiplication  of  the  species.  If,  again,  the  case  is 
that  of  a  metazoon,  there  will  be  the  same  eventual  result. 
An  animal  or  plant  in  which  the  chromatin  is  unequally 
divided  among  the  cells,  must  have  tissues  of  uncertain 
formation.  Assume  that  an  organ  has,  by  survival  of  the 


264  THE  INDUCTIONS  OF  BIOLOGY. 

fittest,  been  adjusted  in  the  proportions  and  qualities  of  its 
parts  to  a  given  function.  If  the  multiplying  protoplasts, 
instead  of  taking  equal  portions  of  chromatin,  have  some  of 
them  smaller  portions,  the  parts  of  the  organ  formed  of 
these,  developing  less  rapidly  and  having  inferior  energies, 
will  throw  the  organ  out  of  adjustment,  and  the  individual 
will  suffer  in  the  struggle  for  life.  That  is  to  say,  irregular 
division  of  the  chromatin  will  introduce  a  deranging  factor 
and  natural  selection  will  weed  out  individuals  in  which  it 
occurs.  Of  course  no  interpretation  is  thus  yielded  of  the 
special  process  known  as  karyokinesis.  Probably  other 
modes  of  equal  division  might  have  arisen.  Here  the  argu- 
ment implies  merely  that  the  tendency  of  evolution  is  to 
establish  some  mode.  In  verification  of  the  view  that  equal 
division  arises  from  the  cause  named,  it  is  pointed  out  to 
me  that  amitosis,  which  is  a  negation  of  mitosis  or  karyo- 
kinesis, occurs  in  transitory  tissues  or  diseased  tissues  or 
where  degeneracy  is  going  on. 

But  how  does  all  this  consist  with  the  conclusion  that  the 
chromatin  conveys  hereditary  traits — that  it  is  the  vehicle  in 
which  the  constitutional  structure,  primarily  of  the  species 
and  secondarily  of  recent  ancestors  and  parents,  is  repre- 
sented? To  this  question  there  seems  to  be  no  definite 
answer.  We  may  say  only  that  this  second  function  is  not 
necessarily  in  conflict  with  the  first.  While  the  unstable 
units  of  chromatin,  ever  undergoing  changes,  diffuse  energy 
around,  they  may  also  be  units  which,  under  the  conditions 
furnished  by  fertilization,  gravitate  towards  the  organization 
of  the  species.  Possibly  it  may  be  that  the  complex  com- 
bination of  proteids,  common  to  chromatin  and  cytoplasm,  is 
that  part  in  which  the  constitutional  characters  inhere; 
while  the  phosphorized  component,  falling  from  its  unstable 
union  and  decomposing,  evolves  the  energy  which,  ordinarily 
the  cause  of  changes,  now  excites  the  more  active  changes 
following  fertilization.  This  suggestion  harmonizes  with  the 
fact  that  the  fertilizing  substance  which  in  animals  consti' 


CELL-LIFE  AND  CELL-MULTIPLICATION.  265 

tutes  the  head  of  the  spermatozoon,  and  in  plants  that  of  the 
spermatozoid  or  antherozoid,  is  distinguished  from  the  other 
agents  concerned  by  having  the  highest  -proportion  of  the 
phosphorized  element;  and  it  also  harmonizes  with  the  fact 
that  the  extremely  active  changes  set  up  by  fertilization  are 
accompanied  by  decrease  of  this  phosphorized  element.  Spe- 
culation aside,  however,  we  may  say  that  the  two  functions  of 
the  chromatin  do  not  exclude  one  another,  but  that  the  general 
activity  which  originates  from  it  may  be  but  a  lower  phase 
of  that  special  activity  caused  by  fertilization.* 

§  74#.  Here  we  come  unawares  to  the  remaining  topic  em- 
braced under  the  title  Cell-Life  and  Cell-Multiplication.  We 
pass  naturally  from  asexual  mutiplication  of  cells  to  sexual 

*  The  writing  of  the  above  section  reminded  me  of  certain  allied  views 
which  I  ventured  to  suggest  nearly  60  years  ago.  They  are  contained  in 
the  Westminster  Review  for  April,  1852,  in  an  article  entitled  "A  Theory 
of  Population  deduced  from  the  General  Law  of  Animal  Fertility."  It  is 
there  suggested  that  the  "  spermatozoon  is  essentially  a  neural  element,  and 
the  ovum  essentially  a  haemal  element,"  or,  as  otherwise  stated,  that  the 
"sperm-cell  is  co-ordinating  matter  and  the  germ-cell  matter  to  be  coordi- 
nated "  (pp.  490-493).  And  along  with  this  proposition  there  is  given  some 
chemical  evidence  tending  to  support  it.  Now  if,  in  place  of  "  neural "  and 
"haemal,"  we  say — the  element  that  is  most  highly  phosphorized  and  the 
element  that  is  phosphorized  in  a  much  smaller  degree ;  or  if,  in  place  of 
co-ordinating  matter  and  matter  to  be  co-ordinated,  we  say — the  matter 
which  initiates  action  and  the  matter  which  is  made  to  act ;  there  is  dis- 
closed  a  kinship  between  this  early  view  and  the  view  just  set  forth.  In  the 
last  part  of  this  work,  "  Laws  of  Multiplication,"  which  is  developed  from  the 
essay  referred  to,  I  left  out  the  portion  containing  the  quoted  sentences,  and 
the  evidence  supporting  the  conclusion  drawn.  Partly  I  omitted  them  because 
the  speculation  did  not  form  an  essential  link  in  the  general  argument,  and 
partly  because  I  did  not  see  how  the  suggested  interpretation  could  hold  of 
plants  as  well  as  of  animals.  If,  however,  the  alleged  greater  staining  capac- 
ity of  the  male  generative  nucleus  in  plants  implies,  as  in  other  cases,  that  the 
male  cell  has  a  larger  proportion  of  the  phosphorized  matter  than  the  other 
elements  concerned,  then  the  difficulty  disappears. 

As,  along  with  the  idea  just  named,  the  dropped  portion  of  the  original 
essay  contains  other  ideas  which  seem  to  me  worth  preserving,  I  have  thought 
it  as  veil  to  reproduce  it,  in  company  with  the  chief  part  of  the  general  argu- 
ment as  at  first  sketched  out.  It  will  be  found  in  Appendix  A  to  this  volume. 


206  THE  INDUCTIONS  OF  BIOLOGY. 

multiplication — from  cell-reproduction  to  cell-generation. 
The  phenomena  are  so  numerous  and  so  varied  that  a  large 
part  of  them  must  be  passed  over.  Conjugation  among  the 
Protopliyta  and  Protozoa,  beginning  with  cases  in  which  there 
is  a  mingling  of  the  contents  of  two  cells  in  no  visible 
respect  different  from  one  another,  and  developing  into  a  great 
variety  of  processes  in  which  they  differ,  must  be  left  aside, 
and  attention  limited  to  the  terminal  process  of  fertilization 
as  displayed  in  higher  types  of  organisms. 

Before  fertilization  there  occurs  in  the  ovum  an  incidental 
process  of  a  strange  kind — "  strange  "  because  it  is  a  col- 
lateral change  taking  no  part  in  subsequent  changes.  I 
refer  to  the  production  and  extrusion  of  the  "  polar  bodies." 
It  is  recognized  that  the  formation  of  each  is  analogous  to 
cell-formation  in  general;  though  process  and  product  are 
both  dwarfed.  Apart  from  any  ascribed  meaning,  the  fact 
itself  is  clear.  There  is  an  abortive  cell-formation.  Abor- 
tiveness  is  seen  firstly  in  the  diminutive  size  of  the  separated 
body  or  cell,  and  secondly  in  the  deficient  number  of  its 
chromosomes:  a  corresponding  deficiency  being  displayed  in 
the  group  of  chromosomes  remaining  in  the  egg — remaining, 
that  is  (on  the  hypothesis  here  to  be  suggested),  in  the 
sister-cell,  supposing  the  polar  body  to  be  an  aborted  cell. 
It  is  currently  assumed  that  the  end  to  be  achieved  by  thus 
extruding  part  of  the  chromosomes,  is  to  reduce  the  re- 
mainder to  half  the  number  characterizing  the  species;  so 
that  when,  to  this  group  in  the  germ-cell,  the  sperm-cell 
brings  a  similarly-reduced  group,  union  of  the  two  shall 
bring  the  chromosomes  to  the  normal  number!  I  venture  to 
suggest  another  interpretation.  In  doing  this,  however,  I  must 
forestall  a  conclusion  contained  in  the  next  chapter;  namely, 
the  conclusion  that  gamogenesis  begins  when  agamogeneois 
is  being  arrested  by  unfavourable  conditions,  and  that  the 
failing  agamogenesis  initiates  the  gamogenesis.  Of  numero  s 
illustrations  to  be  presently  given  I  will,  to  make  clear  t"  e 
conception,  name  only  one — the  formation  of  fructifying 


CELL-LIFE  AND  CELL-MULTIPLICATION.  267 

organs  in  plants  at  times  when,  and  in  places  where,  shoots 
are  falling  off  in  vigour  and  leaves  in  size.  Here  the  suc- 
cessive foliar  organs,  decreasingly  fitted  alike  in  quality  and 
dimensions  for  carrying  on  their  normal  lives,  show  us  an 
approaching  cessation  of  asexual  multiplication,  ending  in 
the  aborted  individuals  we  call  stamens;  and  the  fact  that 
sudden  increase  of  nutrition  while  gamogenesis  is  being 
thus  initiated,  causes  resumption  of  agamogenesis,  shows 
that  the  gamogenesis  is  consequent  upon  the  failing 
agamogenesis.  See  then  the  parallel.  On  going  back 
from  multicellular  organisms  to  unicellular  organisms  (or 
those  homologues  of  them  which  form  the  reproductive 
agents  in  multicellular  organisms),  we  find  the  same  law 
hold.  The  polar  bodies  are  aborted  cells,  indicating  that 
asexual  multiplication  can  no  longer  go  on,  and  that  the 
conditions  leading  to  sexual  multiplication  have  arisen.  If 
this  be  so,  decrease  in  the  chromatin  becomes  an  initial 
cause  of  the  change  instead  of  an  accompanying  incident; 
and  we  need  no  longer  assume  that  a  quantity  of  precious 
matter  is  lost,  not  by  passive  incapacity,  but  by  active  expul- 
sion. Another  anomaly  disappears.  If  from  the  germ-cell 
there  takes  place  this  extrusion  of  superfluous  chromatin,  the 
implication  would  seem  to  be  that  a  parallel  extrusion  takes 
place  from  the  sperm-cell.  But  this  is  not  true.  In  the 
sperm-cell  there  occurs  just  that  failure  in  the  production  of 
chromatin  which,  according  to  the  hypothesis  above  sketched 
out,  is  to  be  expected;  for,  in  the  process  of  cell-multiplica- 
tion, the  cells  which  become  spermatozoa  are  left  with  half 
the  number  of  chromosomes  possessed  by  preceding  cells: 
there  is  actually  that  impoverishment  and  declining  vigour 
here  suggested  as  the  antecedent  of  fertilization.  It  needs 
only  to  imagine  the  ovum  and  the  polar  body  to  be  alike  in 
size,  to  see  the  parallelism ;  and  to  see  that  obscuration  of  it 
arises  from  the  accumulation  of  cytoplasm  in  the  ovum. 

A  test  fact  remains.     Sometimes  the  first  polar  body  ex- 
truded undergoes  fission  while  the  second  is  being  formed. 


268  THE  INDUCTIONS  OF  BIOL.OGY. 

This  can  have  nothing  to  do  with  reducing  the  number  of 
chromosomes  in  the  ovum.  Unquestionably,  however,  this 
change  is  included  with  the  preceding  changes  in  one  trans- 
action, effected  by  one  influence.  If,  then,  it  is  irrelevant  to 
the  decrease  of  chromosomes,  so  must  the  preceding  changes 
be  irrelevant:  the  hypothesis  lapses.  Contrariwise  this  fact 
supports  the  view  suggested  above.  •  That  extrusion  of  a  polar 
body  is  a  process  of  cell-fission  is  congruous  with  the  fact  that 
another  fission  occurs  after  extrusion.  And  that  this  occurs 
irregularly  shows  that  the  vital  activities,  seen  in  cell-growth 
and  cell-multiplication,  now  succeed  in  producing  further 
fission  of  the  dwarfed  cell  and  now  fail :  the  energies  causing 
asexual  multiplication  are  exhausted  and  there  arises  the 
state  which  initiates  sexual  multiplication. 

Maturation  of  the  ovum  having  been  completed,  entrance 
of  the  spermatozoon,  sometimes  through  the  limiting  mem- 
brane and  sometimes  through  a  micropyle  or  opening  in  it, 
takes  place.  This  instantly  initiates  a  series  of  complicated 
changes:  not  many  seconds  passing  before  there  begins  the 
formation  of  an  aster  around  one  end  of  the  spermatozoon- 
head.  The  growth  of  this  aster,  apparently  by  linear 
rangings  of  the  granules  composing  the  reticulum  of  the 
germ-cell,  progresses  rapidly;  while  the  whole  structure 
hence  arising  moves  inward.  Soon  there  takes  place  the 
fusion  of  this  sperm-nucleus  with  the  germ-nucleus  to  form 
the  cleavage-nucleus,  which,  after  a  pause,  begins  to  divide 
and  subdivide  in  the  same  manner  as  cells  at  large:  so 
presently  forming  a  cluster  of  cells  out  of  which  arise  the 
layers  originating  the  embyro.  The  details  of  this  process 
do  not  concern  us.  It  suffices  to  indicate  thus  briefly  its 
general  nature. 

And  now  ending  thus  the  account  of  genesis  under  its 
histological  aspect,  we  pass  to  the  account  of  genesis  under 
its  wider  and  more  significant  aspects. 


CHAPTER  VII. 

GENESIS. 

§  75.  HAVING,  in  the  last  chapter  but  one,  concluded  what 
constitutes  an  individual,  and  having,  in  the  last  chapter, 
contemplated  the  histological  process  which  initiates  a  new 
individual,  we  are  in  a  position  to  deal  with  the  multiplica- 
tion of  individuals.  For  this,  the  title  Genesis  is  here  chosen 
as  being  the  most  comprehensive  title — the  least  specialized 
in  its  meaning.  By  some  biologists  Generation  has  been  used 
to  signify  one  method  of  multiplication,  and  Reproduction 
to  signify  another  method;  and  each  of  these  words  has  been 
thus  rendered  in  some  degree  unfit  to  signify  multiplication 
in  general. 

Here  the  reader  is  indirectly  introduced  to  the  fact  that 
the  production  of  new  organisms  is  carried  on  in  fundament- 
ally unlike  ways.  Up  to  quite  recent  times  it  was  believed, 
even  by  naturalists,  that  all  the  various  processes  of  multi- 
plication observable  in  different  kinds  of  organisms,  have  one 
essential  character  in  common :  it  was  supposed  that  in  every 
species  the  successive  generations  are  alike.  It  has  now 
been  proved,  however,  that  in  many  plants  and  in  numerous 
animals,  the  successive  generations  are  not  alike;  that  from 
one  generation  there  proceeds  another  whose  members  differ 
more  or  less  in  structure  from  their  parents;  that  these 
produce  others  like  themselves,  or  like  their  parents,  or  like 
neither;  but  that  eventually,  the  original  form  re-appears. 


270  THE  INDUCTIONS  OF  BIOLOGY. 

Instead  of  there  being,  as  in  the  cases  most  familiar  to  us,  a 
constant  recurrence  of  the  same  form,  there  is  a  cyclical 
recurrence  of  the  same  form.  These  two  distinct  processes  of 
multiplication,  may  be  aptly  termed  homogenesis  and  hetero- 
genesis.*  Under  these  heads  let  us  consider  them. 

There  are  two  kinds  of  homogenesis,  the  simplest  of  them, 
probably  once  universal  but  now  exceptional,  being  that  in 
which  there  is  no  other  form  of  multiplication  than  one  result- 
ing from  perpetual  spontaneous  fission.  The  rise  of  distinct 
sexes  was  doubtless  a  step  in  evolution,  and  before  it  took 
place  the  formation  of  new  individuals  could  have  arisen 
only  by  division  of  the  old,  either  into  two  or  into  many. 
At  present  this  process  survives,  so  far  as  appears,  among 
Bacteria,  certain  Algce,  and  sundry  Protozoa;  though  it  is 
possible  that  a  rarely-occurring  conjugation  has  in  these  cases 
not  yet  been  observed.  It  is  a  probable  conclusion,  how- 
ever, that  in  the  Bacteria  at  any  rate,  the  once  universal 
mode  of  multiplication  still  survives  as  an  exceptional 
mode.  But  now  passing  over  these  cases,  we  have  to 

note  that  the  kind  of  genesis  (once  supposed  to  be  the  sole 
kind),  in  which  the  successive  generations  are  alike,  is 
sexual  genesis,  or,  as  it  has  been  otherwise  called — gamo- 
genesis.  In  every  species  which  multiplies  by  this  kind  of 
homogenesis,  each  generation  consists  of  males  and  females; 
and  from  the  fertilized  germs  they  produce  the  next  generation 
of  similar  males  and  females  arises :  the  only  needful  qualifi- 
cation of  this  statement  being  that  in  many  Protophyta  and 
Protozoa  the  conjugating  cells  or  protoplasts  are  not  distin- 
guishable in  character.  This  mode  of  propagation  has  the 
further  trait,  that  each  fertilized  germ  usually  gives  rise  to 
but  one  individual — the  product  of  development  is  organized 
round  one  axis  and  not  round  several  axes.  Homogenesis  in 

*  Unfortunately  the  word  heterogenesis  has  been  already  used  as  a  synonym 
for  "  spontaneous  generation."  Save  by  those  few  who  believe  in  "  spontane- 
ous generation,"  however,  little  objection  will  be  felt  to  using  the  word  in  a 
sense  that  seems  much  more  appropriate.  The  meaning  above  given  to  it 
covers  both  Metagenesis  and  Parthenogenesis. 


GENESIS.  271 

contrast  with  heterogenesis  as  exhibited  in  species  which  dis- 
play distinct  sexuality,  has  also  the  characteristic  that  each 
new  individual  begins  as  an  egg  detached  from  the  maternal 
tissues,  instead  of  being  a  portion  of  protoplasm  continuous 
with  them,  and  that  its  development  proceeds  independently. 
This  development  may  be  carried  on  either  internally  or  ex- 
ternally; whence  results  the  division  into  the  oviparous  and 
the  viviparous.  The  oviparous  kind  is  that  in  which  the 
fertilized  germ  is  extruded  from  the  parent  before  it  has 
undergone  any  considerable  development.  The  viviparous 
kind  is  that  in  which  development  is  considerably  advanced, 
or  almost  completed,  before  extrusion  takes  place.  This 
distinction  is,  however,  not  a  sharply-defined  one :  there  are 
transitions  between  the  oviparous  and  the  viviparous  pro- 
cesses. In  ovo-viviparous  genesis  there  is  an  internal  incuba- 
tion ;  and  though  the  young  are  in  this  case  finally  extruded 
from  the  parent  in  the  shape  of  eggs,  they  do  not  leave  the 
parent's  body  until  after  they  have  assumed  something  like 
the  parental  form.  Looking  around,  we  find  that 

homogenesis  is  universal  among  the  Vertebrata.  Every 
vertebrate  animal  arises  from  a  fertilized  germ,  and  unites 
into  its  single  individuality  the  whole  product  of  this 
fertilized  germ.  In  the  mammals  or  highest  Vertebrata,  this 
homogenesis  is  in  every  case  viviparous;  in  birds  it  is  uni- 
formly oviparous;  and  in  reptiles  and  fishes  it  is  always 
essentially  oviparous,  though  there  are  cases  of  the  kind 
above  referred  to,  in  which  viviparity  is  simulated.  Passing 
to  the  Invertebrata,  we  find  oviparous  homogenesis  universal 
among  the  Arachnida  (except  the  Scorpions,  which  are  ovo- 
viviparous)  ;  universal  among  the  higher  Crustacea,  but  not 
among  the  lower;  extremely  general,  though  not  universal, 
among  Insects;  and  universal  among  the  higher  Mollusca 
though  not  among  the  lower.  Along  with  extreme  inferiority 
among  animals,  we  find  homogenesis  to  be  the  exception 
rather  than  the  rule;  and  in  the  vegetal  kingdom  there 
appear  to  be  no  cases,  except  among  the  Algce  and  a  few 


272  THE  INDUCTIONS  OF  BIOLOGY. 

aberrant  parasites  like  the  Rafflesiaccce,  in  which  the  centre 
or  axis  which  arises  from  a  fertilized  germ  becomes  the  im- 
mediate producer  of  fertilized  germs. 

In  propagation  characterized  by  unlikeness  of  the  succes- 
sive generations,  there  is  asexual  genesis  with  occasionally- 
recurring  sexual  genesis ;  in  other  words — agamogcncsis  inter- 
rupted more  or  less  frequently  by  gamogenesis.  If  we  set  out 
with  a  generation  of  perfect  males  and  females,  then,  from 
their  ova  arise  individuals  which  are  neither  males  nor 
females,  but  which  produce  the  next  generation  from  buds. 
By  this  method  of  multiplication  many  individuals  originate 
from  a  single  fertilized  germ.  The  product  of  development  is 
organized  round  more  than  one  centre  or  axis.  The 

simplest  form  of  heterogenesis  is  that  seen  in  most  uniaxial 
plants.  If,  as  we  find  ourselves  obliged  to  do,  we  regard 
each  separate  shoot  or  axis  of  growth  as  a  distinct  indi- 
vidual, homogenesis  is  seen  in  those  which  have  absolutely 
terminal  flowers;  but  in  all  other  uniaxial  plants,  the  suc- 
cessive individuals  are  not  represented  by  the  series  A,  A,  A, 

A,  &c.,  but  they  are  represented  by  the  series  A,  B,  A,  B,  A, 

B,  &c.      For  in  the  majority  of  plants  which  were  classed 
as  uniaxial  (§  50),  and  which  may  be  conveniently  so  dis- 
tinguished from  other  plants,  the  axis  which  shoots  up  from 
the  seed,  and  substantially  constitutes  the  plant,  does  not 
itself  flower  but  gives  lateral  origin  to  flowering  axes.    Though 
in  ordinary  uniaxial  plants  the  fructifying  apparatus  appears 
to  be  at  the  end  of  the  primary,  vertical  axis;   yet  dissection 
shows  that,  morphologically  considered,  each  fructifying  axis 
is  an  offspring  from  the  primary  axis.    There  arises  from  the 
seed  a  sexless  individual,  from  which  spring  by  gemmation 
individuals  having  reproductive  organs ;  and  from  these  there  • 
result  fertilized  germs  or  seeds  that  give  rise  to  sexless  indi- 
viduals.   That  is  to  say,  gamogenesis  and  agamogenesis  alter- 
nate:  the  peculiarity  being  that  the  sexual  individuals  arise 
from   the    sexless    ones    by    continuous    development.      The 
Salpcc  show  us  an  allied  form  of  heterogenesis  in  the  animal 


GENESIS.  273 

kingdom.  Individuals  developed  from  fertilized  ova,  instead 
of  themselves  producing  fertilized  ova,  produce,  by  gemma- 
tion, strings  of  individuals  from  which  fertilized  ova  again 
originate.  In  multiaxial  plants,  we  have  a  succession 

of  generations  represented  by  the  series  A,  B,  B,  B,  &c.,  A,  B, 
B,  B,  &c.  Supposing  A  to  be  a  flowering  axis  or  sexual  indi- 
vidual, then,  from  any  fertilized  germ  it  casts  off,  there  grows 
up  a  sexless  individual,  B;  from  this  there  bud-out  other 
sexless  individuals,  B,  and  so  on  for  generations  more  or  less 
numerous,  until  at  length,  from  some  of  these  sexless  indi- 
viduals, there  bud-out  seed-bearing  individuals  of  the  original 
form  A.  Branched  herbs,  shrubs,  and  trees,  exhibit  this 
form  of  heterogenesis :  the  successive  generations  of  sexless 
individuals  thus  produced  being,  in  most  cases,  continuously 
developed,  or  aggregated  into  a  compound  individual,  but 
being  in  some  cases  discontinuously  developed.  Among 
animals  a  kind  of  heterogenesis  represented  by  the  same  suc- 
cession of  letters,  occurs  in  such  compound  polypes  as  the 
Sertularia,  and  in  those  of  the  Hydrozoa  which  assume -alter- 
nately the  polypoid  form  and  the  form  of  the  Medusa.  The 
chief  differences  presented  by  these  groups  arise  from  the 
fact  that  the  successive  generations  of  sexless  individuals  pro- 
duced by  budding,  are  in  some  cases  continuously  developed, 
and  in  others  discontinuously  developed;  and  from  the  fact 
that,  in  some  cases,  the  sexual  individuals  give  off  their 
fertilized  germs  while  still  growing  on  the  parent-polypedom, 
but  in  other  cases  not  until  after  leaving  the  parent-poly- 
pedom and  undergoing  further  development.  Where, 
as  in  all  the  foregoing  kinds  of  agamogenesis,  the  new  indi- 
viduals bud  out,  not  from  any  specialized  reproductive  organs 
but  from  unspeeialized  parts  of  the  parent,  the  process  has 
been  named,  by  Prof.  Owen,  metagenesis.  In  most  instances 
the  individuals  thus  produced  grow  from  the  outsides  of  the 
parents — the  metagenesis  is  external.  But  there  is  also  a 
kind  of  metagenesis  which  we  may  distinguish  as  internal. 
Certain  entozoa  of  the  genus  Distoma  exhibit  it.  From  the 


274  THE  INDUCTIONS  OP  BIOLOGY. 

egg  of  a  Distoma  there  results  a  rudely-formed  creature  known 
as  a  sporocyst  and  from  this  a  redia.  Gradually,  as  this 
divides  and  buds,  the  greater  part  of  the  inner  substance 
is  transformed  into  young  animals  called  Cercarice  (which 
are  the  larvae  of  Distomata) ;  until  at  length  it  becomes  little 
more  than  a  living  sac  full  of  living  offspring.  In  the  Dis- 
toma pacifica,  the  brood  of  young  animals  thus  arising  by 
internal  gemmation  are  not  Cercarice,  but  are  like  their 
parent :  themselves  becoming  the  producers  of  Cercarice,  after 
the  same  manner,  at  a  subsequent  period.  So  that  now  the 
succession  of  forms  is  represented  by  the  series  A,  B,  A,  B,  &c., 
now  by  the  series  A,  B,  B,  A,  B,  B,  &c.,  and  now  by  A,  B,  B, 
C,  A.  Both  cases,  however,  exemplify  internal  metagenesis 
in  contrast  with  the  several  kinds  of  external  metagenesis 
described  above.  That  agamogenesis  which  is  carried 

on  in  a  reproductive  organ — either  an  ovarium  or  the  homo- 
logue  of  one — has  been  called,  by  Prof.  Owen,  parthenogenesis. 
It  is  the  process  familiarly  exemplified  in  the  Aphides. 
Here,  from  the  fertilized  eggs  laid  by  perfect  females  there 
grow  up  imperfect  females,  in  the  ovaria  of  which  are  de- 
veloped ova  that  though  unfertilized,  rapidly  assume  the 
organization  of  other  imperfect  females,  and  are  born  vivi- 
parously.  From  this  second  generation  of  imperfect  females, 
there  by-and-by  arises,  in  the  same  manner,  a  third  genera- 
tion of  the  same  kind ;  and  so  on  for  many  generations :  the 
series  being  thus  symbolized  by  the  letters  A,  B,  B,  B,  B,  B, 
&c.,  A.  ^Respecting  this  kind  of  heterogenesis  it  should  be 
added  that,  in  animals  as  in  plants,  the  number  of  genera- 
tions of  sexless  individuals  produced  before  the  re-appearance 
of  sexual  ones,  is  indefinite;  both  in  the  sense  that  in  the 
same  species  it  may  go  on  to  a  greater  or  less  extent  accord- 
ing to  circumstances,  and  in  the  sense  that  among  the  genera- 
tions of  individuals  proceeding  from  the  same  fertilized  germ, 
a  recurrence  of  sexual  individuals  takes  place  earlier  in  some 
of  the  diverging  lines  of  multiplication  than  in  others.  In 
trees  we  see  that  on  some  branches  flower-bearing  axes  arise 


GENESIS.  275 

while  other  branches  are  still  producing  only  leaf-bearing 
axes;  and  in  the  successive  generations  of  Aphides  a  parallel 
fact  has  been  observed.  Lastly  has  to  be  set  down 

that  kind  of  heterogenesis  in  which,  along  with  gamogenesis, 
there  occurs  a  form  of  agamogenesis  exactly  like  it,  save  in 
the  absence  of  fecundation.  This  is  called  true  partheno- 
genesis— ^production  carried  on  by  virgin  mothers  which  are 
in  all  respects  like  other  mothers.  Among  silk-worm-moths 
this  parthenogenesis  is  exceptional  rather  than  ordinary. 
Usually  the  eggs  of  these  insects  are  fertilized;  but  if  they 
are  not  they  are  still  laid,  and  some  of  them  produce  larvae. 
In  certain  Lepidoptera,  however,  of  the  groups  Psycliidce  and 
Tineidce,  parthenogenesis  appears  to  be  a  normal  process — 
indeed,  so  far  as  is  known,  the  only  process;  for  of  some 
species  the  males  have  never  been  found. 

A  general  conception  of  the  relations  among  the  different 
modes  of  Genesis,  thus  briefly  described,  will  be  best  given 
by  the  following  tabular  statement. 

f  Oviparous 

or 

f  Homogenesis,  which  is  usually  Gamogenesis  •!  Ovo-viviparous 
.2   I  or 

[  Viviparous 
or 

«  f  Gamogenesis 

O  i     alternating 

Heterogenesis,  which  is  j    with  (  Parthenogenesis 

[  Agamogenesis  \  or  f  Internal 

[  Metagenesis  \       or 

[  External 

This,  like  all  other  classifications  of  such  phenomena,  pre- 
sents anomalies.  It  may  be  justly  objected  that  the  pro- 
cesses here  grouped  under  the  head  agamogenesis,  are  the 
same  as  those  before  grouped  under  the  head  of  discontinuous 
development  (§  50)  :  thus  making  development  and  genesis 
partially  coincident.  Doubtless  it  seems  awkward  that  what 
are  from  one  point  of  view  considered  as  structural  changes 
are  from  another  point  of  view  considered  as  modes  of  multi- 


276  THE  INDUCTIONS  OF  BIOLOGY. 

plication.*  There  is,  however,  nothing  for  us  but  a  choice  of 
imperfections.  We  cannot  by  any  logical  dichotomies  accu- 
rately express  relations  which,  in  Nature,  graduate  into  one 
another  insensibly.  Neither  the  above,  nor  any  other  scheme, 
can  do  more  than  give  an  approximate  idea  of  the  truth. 

§  76.  Genesis  under  every  form  is  a  process  of  negative 
or  positive  disintegration ;  and  is  thus  essentially  opposed  to 
that  process  of  integration  which  is  the  primary  process  in 
individual  evolution.  Negative  disintegration  occurs  in  those 
cases  where,  as  among  the  compound  Hydrozoa,  there  is  a 
continuous  development  of  new  individuals  by  budding  from 
the  bodies  of  older  individuals;  and  where  the  older  indi- 
viduals are  thus  prevented  from  growing  to  a  greater  size,  or 
reaching  a  higher  degree  of  integration.  Positive  disintegra- 
tion occurs  in  those  forms  of  agamogenesis  where  the  produc- 
tion of  new  individuals  is  discontinuous,  as  well  as  in  all  cases 
of  gamogenesis.  The  degrees  of  disintegration  are  various. 
At  the  one  extreme  the  parent  organism  is  completely  broken 
up,  or  dissolved  into  new  individuals;  and  at  the  other 
extreme  each  new  individual  forms  but  a  small  deduction 
from  the  parent  organism.  Protozoa  and  Protopliyta  show 
us  that  form  of  disintegration  called  spontaneous  fission: 
two  or  more  individuals  being  produced  by  the  splitting-up 
of  the  original  one.  The  Volvox  and  the  Hydrodictyon 
are  plants  which,  having  developed  broods  within  themselves, 
give  them  exit  by  bursting;  and  among  animals  the  one 
lately  referred  to  which  arises  from  the  Distoma  egg,  entirely 
loses  its  individuality  in  the  individualities  of  the  numerous 

*  Prof.  Huxley  avoids  this  difficulty  by  making  every  kind  of  Genesis  a 
mode  of  development.  His  classification,  which  suggested  the  one  given 
above,  is  as  follows : — 

f  Growth 
Continuous  •< 

[  Metamorphosis 


Development 


f  Metagenesis 
f  Agamogenesis  < 

Discontinuous  <  (.  Parthenogenesis 

[  Gamogenesis 


GENESIS.  277 

Distoma-l'dTvas  with  which  it  becomes  filled.  Speak- 

ing generally,  the  degree  of  disintegration  becomes  less 
marked  as  we  approach  the  higher  organic  forms.  Plants  of 
superior  types  throw  off  from  themselves,  whether  by  gamo- 
genesis  or  agamogenesis,  parts  that  are  relatively  small; 
and  among  superior  animals  there  is  no  case  in  which  the 
parent  individuality  is  habitually  lost  in  the  production  of 
new  individuals.  To  the  last,  however,  there  is  of 

necessity  a  greater  or  less  disintegration.  The  seeds  and 
pollen-grains  of  a  flowering  plant  are  disintegrated  portions 
of  tissue;  as  are  also  the  ova  and  spermatozoa  of  animals. 
And  whether  the  fertilized  germs  carry  away  from  their 
parents  small  or  large  quantities  of  nutriment,  these  quanti- 
ties in  all  cases  involve  further  negative  or  positive  disinte- 
grations of  the  parents. 

Except  in  spore-producing  plants,  new  individuals  which 
result  from  agamogenesis  usually  do  not  separate  from  the 
parent-individuals  until  they  have  undergone  considerable 
development,  if  not  complete  development.  The  agamo- 
genetic  offspring  of  those  lowest  organisms  which  develop 
centrally,  do  not,  of  course,  pass  beyond  central  structure; 
but  the  agamogenetic  offspring  of  organisms  which  develop 
axially,  commonly  assume  an  axial  structure  before  they  be- 
come independent.  The  vegetal  kingdom  shows  us  this  in 
the  advanced  organization  of  detached  bulbils,  and  of  buds 
that  root  themselves  before  separating.  Of  animals,  the 
Hydrozoa,  the  Trematoda,  and  the  Salpce,  present  us  with 
different  kinds  of  agamogenesis,  in  all  of  which  the  new 
individuals  are  organized  to  a  considerable  extent  before 
being  cast  off.  This  rule  is  not  without  exceptions,  however. 
The  statoblasts  of  the  Plumatella  (which  play  the  part  of 
winter  eggs),  developed  in  an  unspecialized  part  of  the  body, 
furnish  a  case  of  metagenesis  in  which  centres  of  develop- 
ment, instead  of  axes,  are  detached;  and  in  the  above-de- 
scribed parthenogenesis  of  moths  and  bees,  such  centres  are 

detached  from  an  ovarium. 
19 


278  THE  INDUCTIONS  OF  BIOLOGY. 

When  produced  by  gamogenesis,  the  new  individuals  be- 
come (in  a  morphological  sense)  independent  of  the  parents 
while  still  in  the  shape  of  centres  of  development,  rather  than 
axes  of  development;  and  this  even  where  the  reverse  is 
apparently  the  case.  The  fertilized  germs  of  those  inferior 
plants  which  are  central,  or  multicentral,  in  their  develop- 
ment, are  of  course  thrown  off  as  centres;  and  the  same  is 
usually  the  case  even  in  those  which  are  uniaxial  or  multi- 
aiiaL  In  the  higher  plants,  of  the  two  elements  that  go  to 
the  formation  of  the  fertilized  germ,  the  pollen-cell  is  abso- 
lutely separated  from  the  parent-plant  under  the  shape  of  a 
centre,  and  the  egg-cell,  though  not  absolutely  separated  from 
the  parent,  is  still  no  longer  subordinate  to  the  organizing 
forces  of  the  parent.  So  that  when,  after  the  egg-cell  has 
been  fertilized  by  matter  from  the  pollen-tube,  the  develop- 
ment commences,  it  proceeds  without  parental  control:  the 
new  individual,  though  remaining  physically  united  with 
the  old  individual,  becomes  structurally  and  functionally 
separate:  the  old  individual  doing  no  more  than  supply 
materials.  Throughout  the  animal  kingdom,  the  new 

individuals  produced  by  gamogenesis  are  obviously  separated 
in  the  shape  of  centres  of  development  wherever  the  repro- 
duction is  oviparous:  the  only  conspicuous  variation  being 
in  the  quantity  of  nutritive  matter  bequeathed  by  the  parent 
at  the  time  of  separation.  And  though,  where  the  reproduc- 
tion is  viviparous,  the  process  appears  to  be  different,  and 
in  one  sense  is  so,  yet,  intrinsically,  it  is  the  same.  For  in 
these  cases  the  new  individual  really  detaches  itself  from  the 
parent  while  still  only  a  centre  of  development ;  but  instead 
of  being  finally  cast  off  in  this  state  it  is  re-attached,  and 
supplied  with  nutriment  until  it  assumes  a  more  or  less  com- 
plete axial  structure. 

|  77.  As  we  have  lately  seen,  the  essential  act  in  gamo- 
genesis is  the  union  of  two  cell-nuclei,  produced  in  the  great 
majority  of  cases  by  different  parent  organisms.  Nearly 


GENESIS.  279 

always  the  containing  cells,  often  called  gametes,  are  unlike : 
the  sperm-cell  being  the  male  product,  and  the  germ-cell  the 
female.  But  among  some  Protozoa  and  many  of  the  lower 
Alga  and  Fungi,  the  uniting  cells  show  no  differentiation. 
Sexuality  is  only  nascent. 

There  are  very  many  modes  and  modifications  of  modes  in 
which  these  cells  are  produced;  very  many  modes  and 
modifications  of  modes  by  which  they  are  brought  into 
contact;  and  very  many  modes  and  modifications  of  modes 
by  which  the  resulting  fertilized  germs  have  secured  to  them 
the  fit  conditions  for  their  development.  But  passing  over 
these  divergent  and  re-divergent  kinds  of  sexual  multiplica- 
tion, which  it  would  take  too  much  space  here  to  specify,  the 
one  universal  trait  is  this  coalescence  of  a  detached  portion 
of  one  organism  with  a  more  or  less  detached  portion  of 
another. 

Such  simple  Algce  as  the  Desmidiece,  which  are  sometimes 
called  unicellular  plants,  show  us  a  coalescence,  not  of  de- 
tached portions  of  two  organisms,  but  of  two  entire  organ- 
isms: the  entire  contents  of  the  individuals  uniting  to  form 
the  germ-mass.  Where,  as  among  the  Confervoidece,  we  have 
aggregated  cells  whose  individualities  are  scarcely  at  all 
subordinate  to  that  of  the  aggregate,  the  gamogenetic  act  is 
often  effected  by  the  union  "  of  separate  motile  protoplasmic 
masses  produced  by  the  division  of  the  contents  of  any  cell 
of  the  aggregate.  These  free-swimming  masses  of  proto- 
plasm, which  are  quite  similar  to  (but  generally  smaller 
than)  the  agamogenetic  '  zoospores '  of  the  same  plants,  and 
to  the  free-swimming  individuals  of  many  Protophyta,  are 
apparently  the  primitive  type  of  gametes  (conjugating  cells)  ; 
but  it  is  noteworthy  that  such  a  gamete  nearly  always  unites 
with  one  derived  from  another  cell  or  from  another  indivi- 
dual. The  same  fact  holds  with  regard  to  the  gametes  of  the 
Protophytes  themselves,  which  are  formed  in  the  same  way 
from  the  single  cell  of  the  mother  individual.  In  the  higher 
types  of  Conferroidece,  and  in  Vaucheria,  we  find  these  equi- 


280  THE  INDUCTIONS  OF  BIOLOGY. 

valcnt,  free-swimming,  gametes  replaced  by  sexually  dif- 
ferentiated sperm-  and  germ-cells,  in  some  cases  arising  in 
different  organs  set  apart  for  their  production,  and  essentially 
representing  those  found  in  the  higher  plants.  Transitional 
forms,  intermediate  between  these  and  the  cases  where 
equivalent  gametes  are  formed  from  any  cell  of  the  plant  are 
also  known." 

Recent  investigations  concerning  the  conjugation  of  Pro- 
tozoa have  shown  that  there  is  not,  as  was  at  one  time  thought, 
a  fusion  of  two  individualities,  but  a  fusion  of  parts  of  their 
nuclei.  The  macro-nucleus  having  disappeared,  and  the 
micro-nucleus  having  broken  up  into  portions,  each  individual 
receives  from  the  other  one  of  these  portions,  which  becomes 
fused  with  its  own  nuclear  matter.  So  that  even  in  these 
humble  forms,  where  there  is  no  differentiation  of  sexes,  the 
union  is  not  between  elements  that  have  arisen  in  the  same 
individual  but  between  those  which  have  arisen  in  different 
individuals :  the  parts  being  in  this  case  alike. 

The  marvellous  phenomena  initiated  by  the  meeting  of 
sperm-cell  and  germ-cell,  or  rather  of  their  nuclei,  naturally 
suggest  the  conception  of  some  quite  special  and  peculiar 
properties  possessed  by  these  cells.  It  seems  obvious  that 
this  mysterious  power  which  they  display  of  originating  a 
new  and  complex  organism,  distinguishes  them  in  the 
broadest  way  from  portions  of  organic  substance  in  general. 
Nevertheless,  the  more  we  study  the  evidence  the  more  are 
we  led  towards  the  conclusion  that  these  cells  are  not 
fundamentally  different  from  other  cells.  The  first 

fact  which  points  to  this  conclusion  is  the  fact  recently 
dwelt  upon  (§  G3),  that  in  many  plants  and  inferior  animals, 
a  small  fragment  of  tissue  which  is  but  little  differentiated, 
is  capable  of  developing  into  an  organism  like  that  from 
which  it  was  taken.  This  implies  that  the  component  units 
of  tissues  have  inherent  powers  of  arranging  themselves  into 
the  forms  of  the  organisms  which  originated  them.  And 
if  in  these  component  units,  which  we  distinguished  as 


GENESIS.  281 

physiological,  such  powers  exist, — if,  under  fit  conditions, 
and  when  not  much  specialized,  they  manifest  such  powers  in 
a  way  as  marked  as  that  in  which  the  contents  of  sperm-cells 
and  germ-cells  manifest  them;  then,  it  becomes  clear  that 
the  properties  of .  sperm-cells  and  germ-cells  are  not  so 
peculiar  as  we  are  apt  to  assume.  Again,  the  organs 

emitting  sperm-cells  and  germ-cells  have  none  of  the  special- 
ities of  structure  which  might  be  looked  for,  did  sperm-cells 
and  germ-cells  need  endowing  with  properties  unlike  those 
of  all  other  organic  agents.  On  the  contrary,  these  reproduc- 
tive centres  proceed  from  tissues  characterized  by  their  low 
organization.  In  plants,  for  example,  it  is  not  appendages 
that  have  acquired  considerable  structure  which  produce  the 
fructifying  particles:  these  arise  at  the  extremities  of  the 
axes  where  the  degree  of  structure  is  the  least.  The  cells 
out  of  which  come  the  egg  and  the  pollen-grains,  are  formed 
from  undifferentiated  tissue  in  the  interior  of  the  ovule  and 
of  the  stamen.  Among  many  inferior  animals  devoid  of 
special  reproductive  organs,  such  as  the  Hydra,  the  ova  and 
spermatozoa  originate  from  the  interstitial  cells  of  the  ecto- 
derm, which  lie  among  the  bases  of  the  functional  cells — 
have  not  been  differentiated  for  function ;  and  in  the  Medusas, 
according  to  Weismann,  they  arise  in  the  homologous  layer, 
save  where  the  medusoid  form  remains  attached,  and  then 
they  arise  in  the  endoderm  and  migrate  to  the  ectoderm : 
lack  of  specialization  being  in  all  cases  implied.  Then  in 
the  higher  animals  these  same  generative  agents  appear  to 
be  merely  modified  epithelium-cells — cells  not  remarkable 
for  their  complexity  of  structure  but  rather  for  their  sim- 
plicity. If,  by  way  of  demurrer  to  this  view,  it  be  asked 
why  other  epithelium-cells  do  not  exhibit  like  properties ;  there 
are  two  replies.  The  first  is  that  other  epithelium-cells  are 
usually  so  far  changed  to  fit  them  to  their  special  functions 
that  they  are  unfitted  for  assuming  the  reproductive  function. 
The  second  is  that  in  some  cases,  w'.iere  they  are  but  little 
specialized,  they  do  exhibit  the  like  properties :  not,  indeed, 


282  THE  INDUCTIONS  OP  BIOLOGY. 

by  uniting  with  other  cells  to  produce  new  germs  but  by  pro- 
ducing new  germs  without  such  union.  I  learn  from  Dr. 
Hooker  that  the  Begonia  phyllomaniaca  habitually  develops 
young  plants  from  the  scales  of  its  stem  and  leaves — nay, 
that  many  young  plants  are  developed  by  a  single  scale.  The 
epidermal  cells  composing  one  of  these  scales  swell,  here  and 
there,  into  large  globular  cells;  form  chlorophyll  in  their 
interiors;  shoot  out  rudimentary  axes;  and  then,  by  spon- 
taneous constrictions,  cut  themselves  off ;  drop  to  the  ground ; 
and  grow  into  Begonias.  Moreover,  in  a  succulent  English 
plant,  the  Malaxis  paludosa,  a  like  process  occurs:  the  self- 
detached  cells  being,  in  this  case,  produced  by  the  surfaces  of 
the  leaves.*  Thus,  there  is  no  warrant  for  the  assump- 

tion that  sperm-cells  and  germ-cells  possess  powers  funda- 
mentally unlike  those  of  other  cells.  The  inference  to  which 
the  facts  point,  is,  that  they  differ  from  the  rest  mainly  in 
not  having  undergone  functional  adaptations.  They  are  cells 
which  have  departed  but  little  from  the  original  and  most 
general  type :  such  specializations  as  some  of  them  exhibit  in 
the  shape  of  locomotive  appliances,  being  interpretable  as  ex- 
trinsic modifications  which  have  reference  to  nothing  beyond 
certain  mechanical  requirements.  Sundry  facts  tend 

likewise  to  show  that  there  does  not  exist  the  profound 
distinction  we  are  apt  to  assume  between  the  male  and 
female  reproductive  elements.  In  the  ,  common  polype 
sperm-cells  and  germ-cells  are  developed  in  the  same  layer  of 

*  The  implication  is  that  an  essentially  similar  process  occurs  in  those 
fragments  of  leaves  used  for  artificial  propagation.  Besides  the  Begonias 
in  general,  I  learn  that  various  other  plants  are  thus  multiplied — Citron 
and  orange  trees,  ffoya  carnosa,  Aucuba  japonica,  Clianthits  puniceus, 
etc.,  etc.  Bryophyllum  calicinwn,  Rochea  falcata,  and  Echeveria.  I  also 
learn  that  the  following  plants,  among  others,  produce  buds  from  their 
foliage  leaves: — Cardamine  pratensis.  Nasturtium  officinaie,  Roripa  palus- 
tris,  Eras&ica  oleracea,  Arabis  pumila,  Chelidonium  majus,  Nymph<xa  guiancn- 
sis,  Episcia  bicolor,  Chirita  sivensis,  Pinguicula  Backcri,  Allium,  Gagea, 
Tolmia,  Frifillaria,  Ornithogalum,  etc.  In  Cardamine  and  several  others,  a 
complete  miniature  plant  is  at  once  produced ;  in  other  cases  bulbils  or  simi- 
lar detachable  buds. 


GENESIS.  283 

indifferent  tissue;  and  in  Tethya,  one  of  the  sponges,  Prof. 
Huxley  has  observed  that  they  occur  mingled  together  in  the 
general  parenchyma.  The  pollen-grains  and  embryo-cells  of 
plants  arise  in  adjacent  parts  of  the  meristematic  tissue  of 
the  flower-bud;  and  from  the  description  of  a  monstrosity  in 
the  Passion-flower,  recently  given  by  Mr.  Salter  to  the  Lin- 
naean  Society,  it  appears  both  that  ovules  may,  in  their  gen- 
eral structure,  graduate  into  anthers,  and  that  they  may 
produce  pollen  in  their  interiors.  Moreover,  among  the  lower 
Algce,  which  show  the  beginning  of  sexual  differentiation, 
the  smaller  gametes,  which  we  must  regard  as  incipient  sperm- 
cells,  are  sometimes  able  to  fuse  inter  se,  and  give  rise  to  a- 
zygote  which  will  produce  a  new  plant.  All  which  evidence 
is  in  perfect  harmony  with  the  foregoing  conclusion;  since, 
if  sperm-cells  and  germ-cells  have  natures  not  essentially  un- 
like those  of  unspecialized  cells  in  general,  their  natures 
cannot  be  essentially  unlike  each  other. 

The  next  general  fact  to  be  noted  is  that  these  cells  whose 
union  constitutes  the  essential  act  of  gamogenesis,  are  cells 
in  which  the  developmental  changes  have  come  to  a  close — 
cells  which  are  incapable  of  further  evolution.  Though  they 
are  not,  as  many  cells  are,  unfitted  for  growth  and  meta- 
morphosis by  being  highly  specialized,  yet  they  have  lost  the 
power  of  growth  and  metamorphosis.  They  have  severally 
reached  a  state  of  equilibrium.  And  while  the  internal 
balance  of  forces  prevents  a  continuance  of  constructive 
changes,  it  is  readily  overthrown  by  external  destructive  forces. 
For  it  almost  uniformly  happens  that  sperm-cells  and  germ- 
cells  which  are  not  brought  in  contact  disappear.  In  a  plant, 
the  egg-cell,  if  not  fertilized,  is  absorbed  or  dissipated,  while 
the  ovule  aborts;  and  the  unimpregnated  ovum  eventually 
decomposes :  save,  indeed,  in  those  types  in  which  partheno- 
genesis is  a  part  of  the  normal  cycle. 

Such  being  the  characters  of  these  cells,  and  such  being 
their  fates  if  kept  apart,  we  have  now  to  observe  what 
happens  when  they  are  united.  In  plants  the  extremity 


284  THE  INDUCTIONS  OF  BIOLOGY. 

of  the  elongated  pollen-cell  applies  itself  to  the  surface  of 
the  embryo-sac,  and  one  of  its  nuclei  having,  with  some 
protoplasm,  passed  into  the  egg-cell,  there  becomes  fused 
with  the  nucleus  of  the  egg-cell.  Similarly  in  animals,  the 
spermatozoon  passes  through  the  limiting  membrane  of  the 
ovum,  and  a  mixture  takes  place  between  the  substance 
of  its  nucleus  and  the  substance  of  the  nucleus  of  the 
ovum.  But  the  important  fact  which  it  chiefly 

concerns  us  to  notice,  is  that  on  the  union  .of  these  re- 
productive elements  there  begins,  either  at  once  or  on  the 
return  of  favourable  conditions,  a  new  series  of  develop- 
mental changes.  The  state  of  equilibrium  at  which  each 
had  arrived  is  destroyed  by  their  mutual  influence,  and  the 
constructive  changes,  which  had  come  to  a  close,  recommence. 
A  process  of  cell-multiplication  is  set  up;  and  the  resulting 
cells  presently  begin  to  aggregate  into  the  rudiment  of  a  new 
organism. 

Thus,  passing  over  the  variable  concomitants  of  gamo- 
genesis,  and  confining  our  attention  to  what  is  constant  in  it, 
we  see: — that  there  is  habitually,  if  not  universally,  a  fusion 
of  two  portions  of  organic  substance  which  are  either  them- 
selves distinct  individuals,  or  are  thrown  off  by  distinct  in- 
dividuals; that  these  portions  of  organic  substance,  which 
are  severally  distinguished  by  their  low  degree  of  special- 
ization, have  arrived  at  states  of  structural  quiescence  or 
equilibrium;  that  if  they  are  not  united  this  equilibrium 
ends  in  dissolution;  but  that  by  the  mixture  of  them  this 
equilibrium  is  destroyed  and  a  new  evolution  initiated. 

§  78.  What  are  the  conditions  under  which  Genesis  takes 
place?  How  does  it  happen  that  some  organisms  multiply 
by  homogenesis  and  others  by  heterogenesis  ?  Why  is  it 
that  where  agamogenesis  prevails  it  is  usually  from  time  to 
time  interrupted  by  gamogenesis?  A  survey  of  the  facts 
discloses  certain  correlations  which,  if  not  universal,  are  too 
general  to  be  without  significance. 


GENESIS.  285 

Where  multiplication  is  carried  on  by  heterogenesis  we 
find,  in  numerous  cases,  that  agamogenesis  continues  as  long 
as  the  forces  which  result  in  growth  are  greatly  in  excess  of 
the  antagonist  forces.  Conversely,  we  find  that  the  recur- 
rence of  gamogenesis  takes  place  when  the  conditions  are 
no  longer  so  favourable  to  growth.  In  like  manner  where 
there  is  homogenetic  multiplication,  new  individuals  are  usu- 
ally not  formed  while  the  preceding  individuals  are  still 
rapidly  growing — that  is,  while  the  forces  producing  growth 
exceed  the  opposing  forces  to  a  great  extent;  but  the  forma- 
tion of  new  individuals  begins  when  nutrition  is  nearly 
equalled  by  expenditure.  A  few  out  of  the  many  facts  which 
seem  to  warrant  these  inductions  must  suffice. 

The  relation  in  plants  between  fructification  and  innu- 
trition (or  rather,  between  fructification  and  such  diminished 
nutrition  as  makes  growth  relatively  slow)  was  long  ago 
asserted  by  a  German  biologist — Wolff,  I  am  told.  Since 
meeting  with  this  assertion  I  have  examined  into  the  facts 
for  myself.  The  result  has  been  a  conviction,  strengthened  by 
every  inquiry,  that  some  such  relation  exists.  TJniaxial 

plants  begin  to  produce  their  lateral,  flowering  axes,  only 
after  the  main  axis  has  developed  the  great  mass  of  its 
leaves,  and  is  showing  its  diminished  nutrition  by  smaller 
leaves,  or  shorter  internodes,  or  both.  In  multiaxial  plants 
two,  three,  or  more  generations  of  leaf-bearing  axes,  or  sex- 
less individuals,  are  produced  before  any  seed-bearing  indi- 
viduals show  themselves.  When,  after  this  first  stage  of  rapid 
growth  and  agamogenetic  multiplication,  some  gamogenetic 
individuals  arise,  they  do  so  where  the  nutrition  is  least ; — not 
on  the  main  axis,  or  on  secondary  axes,  or  even  on  tertiary 
axes,  but  on  axes  that  are  the  most  removed  from  the 
channels  which  supply  nutriment.  Again,  a  flowering  axis 
is  commonly  less  bulky  than  the  others:  either  much 
shorter  or,  if  long,  much  thinner.  And  further,  it  is  an 
axis  of  which  the  terminal  internodes  are  undeveloped:  the 
foliar  organs,  which  instead  of  becoming  leaves  become 


286  THE  INDUCTIONS  OP  BIOLOGY. 

sepals,  and  petals,  and  stamens,  follow  each  other  in  close 
succession,  instead  of  being  separated  by  portions  of  the  still- 
growing  axis.  Another  group  of  evidences  meets  us 
when  we  observe  the  variations  of  fruit-bearing  which  accom- 
pany variations  of  nutrition  in  the  plant  regarded  as  a  whole. 
Besides  finding,  as  above,  that  gamogenesis  commences  only 
when  growth  has  been  checked  by  extension  of  the  remoter 
parts  to  some  distance  from  the  roots,  we  find  that  gamo- 
genesis is  induced  at  an  earlier  stage  than  usual  by  checking 
the  nutrition.  Trees  are  made  to  fruit  while  still  quite 
small  by  cutting  their  roots  or  putting  them  into  pots;  and 
luxuriant  branches  which  have  had  the  flow  of  sap  into  them 
diminished,  by  what  gardeners  call  "  ringing,"  begin  to  pro- 
duce flower-shoots  instead  of  leaf-shoots.  Moreover,  it  is  to 
be  remarked  that  trees  which,  by  flowering  early  in  the  year, 
seem  to  show  a  direct  relation  between  gamogenesis  and  in- 
creasing nutrition,  really  do  the  reverse;  for  in  such  trees 
the  flower-buds  are  formed  in  the  autumn..  That  structure 
which  determines  these  buds  into  sexual  individuals  is  given 
when  the  nutrition  is  declining.  Conversely,  very 
high  nutrition  in  plants  prevents,  or  arrests,  gamogenesis. 
It  is  notorious  that  unusual  richness  of  soil,  or  too  large  a 
quantity  of  manure,  results  in  a  continuous  production  of 
leaf -bearing  or  sexless  shoots;  and  a  like  result  happens 
when  the  cutting  down  of  a  tree,  or  of  a  large  part  of  it,  is 
followed  by  the  sending  out  of  new  shoots:  these,  supplied 
with  excess  of  sap,  are  luxuriant  and  sexless.  Besides  being 
prevented  from  producing  sexual  individuals  by  excessive 
nutrition,  plants  are,  by  excessive  nutrition,  made  to  change 
the  sexual  individuals  they  were  about  to  produce,  into  sexless 
ones.  This  arrest  of  gamogenesis  may  be  seen  in  various 
stages.  The  familiar  instance  of  flowers  made  barren  by  the 
transformation  of  their  stamens  into  petals,  shows  us  the 
lowest  degree  of  this  reversed  metamorphosis.  Where  the 
petals  and  stamens  are  partially  changed  into  green  leaves, 
the  return  towards  the  agamogenetic  structure  is  more 


GENESIS.  287 

marked;  and  it  is  still  more  marked  when,  as  occasionally 
happens  in  luxuriantly-growing  plants,  new  flowering  axes, 
and  even  leaf-bearing  axes,  grow  out  of  the  centres  of 
flowers.*  The  anatomical  structure  of  the  sexual  axis 

affords  corroborative  evidence :  giving  the  impression,  as  it 
does,  of  an  aborted  sexless  axis.  Besides  lacking  those  inter- 

*  Among  various  examples  I  have  observed,  the  most  remarkable  were 
among  Foxgloves,  growing  in  great  numbers  and  of  large  size,  in  a  wood 
between  Whatstandwell  Bridge  and  Crich,  in  Derbyshire.  In  one  case  the 
lowest  flower  on  the  stem  contained,  in  place  of  a  pistil,  a  shoot  or  spike  of 
flower-buds,  similar  in  structure  to  the  embryo-buds  of  the  main  spike.  I 
counted  seventeen  buds  on  it ;  of  which  the  first  had  three  stamens,  but 
was  otherwise  normal;  the  second  had  three;  the  third,  four;  the  fourth, 
four ;  &c.  Another  plant,  having  more  varied  monstrosities,  evinced  excess 
of  nutrition  with  equal  clearness.  The  following  arc  the  notes  I  took  of  its 
structure: — 1st,  or  lowest  flower  on  the  stem,  very  large;  calyx  containing 
eight  divisions,  one  partly  transfprmed  into  a  corolla,  and  another  trans- 
formed into  a  small  bud  with  bract  (this  bud  consisted  of  a  five-cleft  calyx, 
four  sessile  anthers,  a  pistil,  and  a  rudimentary  corolla) ;  the  corolla  of  the 
main  flower,  which  was  complete,  contained  six  stamens,  three  of  them 
bearing  anthers,  two  others  being  flattened  and  coloured,  and  one  rudiment- 
ary ;  there  was  no  pistil  but,  in  place  of  it,  a  large  bud,  consisting  of  a  three- 
cleft  calyx  of  which  two  divisions  were  tinted  at  the  ends,  an  imperfect 
corolla  marked  internally  with  the  usual  purple  spots  and  hairs,  three 
anthers  sessile  on  this  mal-formed  corolla,  a  pistil,  a  seed  vessel  with  ovules, 
and,  growing  to  it,  another  bud  of  which  the  structure  was  indistinct.  2nd 
flower,  large;  calyx  of  seven  divisions,  one  being  transformed  into  a  bud 
with  bract,  but  much  smaller  than  the  other ;  corolla  large  but  cleft  along  the 
top ;  six  stamens  with  anthers,  pistil,  and  seed-vessel.  3rd  flower,  large ; 
six-cleft  calyx,  cleft  corolla,  with  six  stamens,  pistil,  and  seed-vessel,  with  a 
second  pistil  half  unfolded  at  its  apex.  4th  flower,  large ;  divided  along  the 
top,  six  stamens.  5th  flower,  large;  corolla  divided  into  three  parts,  six 
stamens.  6th  flower,  large;  corolla  cleft,  calyx  six  cleft,  the  rest  of  the 
flower  normal.  7th,  and  all  succeeding  flowers,  normal. 

While  this  chapter  is  under  revision,  another  noteworthy  illustration  has 
been  furnished  to  me  by  a  wall-trained  pear  tree  which  was  covered  in  the 
spring  by  luxuriant  "foreright"  shoots.  As  I  learned  from  the  gardener,  it 
was  pruned  just  as  the  fruit  was  setting.  A  large  excess  of  sap  was  thus  thrown 
into  other  branches,  with  the  result  that  in  a  number  of  them  the  young  pears 
were  made  monstrous  by  reversion.  In  some  cases,  instead  of  the  dried  up 
sepals  at  the  top  of  the  pear,  there  were  produced  good  sized  leaves ;  and  in 
other  cases  the  seed-bearing  core  of  the  pear  was  transformed  into  a  growth 
which  protruded  through  the  top  of  the  pear  in  the  shape  of  a  new  shoot. 


288  THE  INDUCTIONS  OF  BIOLOGY. 

nodes  which  the  leaf-bearing  axis  commonly  possesses,  the 
flowering  axis  differs  by  the  absence  of  rudimentary  lateral 
axes.  In  a  leaf-bearing  shoot  the  axil  of  every  leaf  usually 
contains  a  small  bud,  which  may  or  may  not  develop  into  a 
lateral  shoot;  but  though  the  petals  of  a  flower  are  homo- 
logous with  leaves,  they  do  not  bear  homologous  buds  at 
their  bases.  Ordinarily,  too,  the  foliar  appendages  of  sexual 
axes  are  much  smaller  than  those  of  sexless  ones — the 
stamens  and  pistils  especially,  which  are  the  last  formed, 
being  extremely  dwarfed;  and  it  may  be  that  the  absence  of 
chlorophyll  from  the  parts  of  fructification  is  a  fact  of  like 
meaning.  Moreover,  the  formation  of  the  seed-vessel  appears 
to  be  a  direct  consequence  of  arrested  nutrition.  If  a  gloved- 
finger  be  taken  to  represent  a  growing  shoot,  (the  finger 
standing  for  the  pith  of  the  shoot  and  the  glove  for  the  peri- 
pheral layers  of  meristem  and  young  tissue,  in  which  the 
process  of  growth  takes  place) ;  and  if  it  be  supposed  that 
there  is  a  diminished  supply  of  material  for  growth ;  then,  it 
seems  a  fair  inference  that  growth  will  first  cease  at  the  apex 
of  the  axis,  represented  by  the  end  of  the  glove-finger;  and 
supposing  growth  to  continue  in  those  parts  of  the  peripheral 
layers  of  young  tissue  that  are  nearer  to  the  supply  of  nutri- 
ment, their  further  longitudinal  extension  will  lead  to  the 
formation  of  a  cavity  at  the  extremity  of  the  shoot,  like  that 
which  results  in  a  glove-finger  when  the  finger  is  partially 
withdrawn  and  the  glove  sticks  to  its  end.  Whence  it  seems, 
both  that  this  introversion  of  the  apical  meristem  may  be 
considered  as  due  to  failing  nutrition,  and  that  the  ovules 
growing  from  its  introverted  surface  (which  would  have  been 
its  outer  surface  but  for  the  defective  nutrition)  are  extremely 
aborted  homologues  of  external  appendages :  both  they  and 
the  pollen-grains  being  either  morphologically  or  literally 
quite  terminal,  and  the  last  showing  by  their  dehiscence  the 
exhaustion  of  the  organizing  power.* 

*  In  partial  verification,  Mr.  Tansley  writes: — "Prof.  Klebs  of  Basel  has 
shown  that  in  Hydrodictyon,  gametes  can  only  be  produced  by  the  cells  of 


GENESIS.  289 

Those  kinds  of  animals  which  multiply  by  heterogenesis, 
present  us  with  a  parallel  relation  between  the  recurrence  of 
gamogenesis  and  the  recurrence  of  conditions  checking  rapid 
growth:  at  least,  this  is  shown  where  experiments  have 
thrown  light  on  the  connexion  of  cause  and  effect;  namely, 
among  the  Aphides.  These  creatures,  hatched  from  eggs  in 
the  spring,  multiply  by  agamogenesis,  which  in  this  case  is 
parthenogenesis,  throughout  the  summer.  When  the  weather 
becomes  cold  and  plants  no  longer  afford  abundant  sap,  per- 
fect males  and  females  are  produced;  and  from  gamogenesis 
result  fertilized  ova.  But  beyond  this  evidence  we  have 
much  more  conclusive  evidence.  For  it  has  been  shown, 
both  that  the  rapidity  of  the  agamogenesis  is  proportionate 
to  the  warmth  and  nutrition,  and  that  if  the  temperature  and 
supply  of  food  be  artificially  maintained,  the  agamogenesis 
continues  through  the  winter.  Nay  more — it  not  only,  under 
these  conditions,  continues  through  one  winter,  but  it  has 
been  known  to  continue  for  four  successive  years:  some 
forty  or  fifty  sexless  generations  being  thus  produced.  And 
those  who  have  investigated  the  matter  see  no  reason  to 
doubt  the  indefinite  continuance  of  this  agamogenetic  mul- 
tiplication, so  long  as  the  external  requirements  are  duly 
met.  Evidence  of  another  kind,  complicated  by 

a  net  when  these  are  above  a  certain  size  and  age;  and  then  only  under 
conditions  unfavourable  to  growth,  such  as  a  feeble  light  or  poverty  of 
nutritive  inorganic  salts  or  absence  of  oxygen,  or  a  low  temperature  in  the 
water  containing  the  plant.  The  presence  of  organic  substances,  especially 
sugar,  also  acts  as  a  stimulus  to  the  formation  of  gametes,  and  this  is  also 
the  case  in  Vaucheria.  Many  other  Algce  produce  gametes  mainly  at  the 
end  of  the  vegetative  season,  when  food  is  certainly  difficult  to  obtain  in  their 
natural  habitat,  and  we  may  well  suppose  that  thT->  assimilative  power  is 
waning.  Where,  however,  as  is  the  case  in  Vaucheria,  the  plant  depends  for 
propagation  mainly  on  the  production  of  fertilized  eggs,  we  find  the  sexual 
organs  often  produced  in  conditions  very  favourable  to  vegetative  growth, 
in  opposition  to  those  cases  such  as  Hydrodictyon,  where  the  chief  means 
of  propagation  is  by  zoospores.  So  that  side  by  side  with,  and  to  some 
extent  obscuring,  the  principle  developed  above  we  have  a  clear  adaptation  of 
the  production  of  reproductive  cells  to  the  special  circumstances  of  the  case." 


290  THE  INDUCTIONS  OF   BIOLOGY. 

special  influences,  is  furnished  by  the  heterogenesis  of  the 
Daphnia — a  small  crufetacean  commonly  known  as  the 
Water-flea,  which  inhabits  ponds  and  ditches.  From  the 
nature  of  its  habitat  this  little  creature  is  exposed  to  very 
variable  conditions.  Besides  being  frozen  in  winter,  the 
small  bodies  of  water  in  which  it  lives  are  often  unduly 
heated  by  the  summer  Sun,  or  dried  up  by  continued  drought. 
The  circumstances  favourable  to  the  Daphnia's  life  and 
growth,  being  thus  liable  to  interruptions  which,  in  our  cli- 
mate, have  a  regular  irregularity  of  recurrence;  we  may,  in 
conformity  with  the  hypothesis,  expect  to  find  both  that  the 
gamogenesis  recurs  along  with  declining  physical  prosperity 
and  that  its  recurrence  is  very  variable.  I  use  the  expres- 
sion "  declining  physical  prosperity  "  advisedly ;  since  "  de- 
clining nutrition,"  as  measured  by  supply  of  food,  does  not 
cover  all  the  conditions.  This  is  shown  by  the  experiments 
of  Weismann  (abstracted  for  me  by  Mr.  Cunningham)  who 
found  that  in  various  Daphnidece  which  bring  forth  resting 
eggs,  sexual  and  asexual  reproduction  go  on  simultaneously, 
as  well  as  separately,  in  the  spring  and  summer:  these 
variable  results  being  adapted  to  variable  conditions.  For  not 
only  are  these  creatures  liable  to  die  from  lack  of  food,  from 
the  winter's  cold,  and  from  the  drying  up  of  their  ditches,  &c., 
as  well  as  from  the  over-heating  of  them,  but  during  this 
period  of  over-heating  they  are  liable  to  die  from  that  de- 
oxygenation  of  the  water  which  heat  causes.  Manifestly  the 
favourable  and  unfavourable  conditions  recurring  in  com- 
binations that  are  rarely  twice  alike,  cannot  be  met  by  any 
regularly  recurring  form  of  heterogenesis;  and  it  is  interest- 
ing to  see  how  survival  of  the  fittest  has  established  a  mixed 
form.  In  the  spring,  as  well  as  in  the  autumn,  there  is  in 
some  cases  a  formation  of  resting  or  winter  eggs;  and 
evidently  these  provide  against  the  killing  off  of  the  whole 
population  by  summer  drought.  Meanwhile,  by  ordinary 
males  and  females  ijiere  is  a  production  of  summer  eggs 
adapted  to  meet  the  incident  of  drying  up  by  drought  and 


GENESIS.  291 

subsequent  re-supply  of  water.  And  all  along  successive 
generations  of  parthenogenetic  females  effect  a  rapid  multi- 
plication as  long  as  conditions  permit.  Since  life  and  growth 
are  impeded  or  arrested  not  by  lack  of  food  only,  but  by  other 
unfavourable  conditions,  we  may  understand  how  change  in 
one  or  more  of  these  may  set  up  one  or  other  form  of  genesis, 
and  how  the  mixture  of  them  may  cause  a  mixed  mode  of 
multiplication  which,  originally  initiated  by  external  causes, 
becomes  by  inheritance  and  selection  a  trait  of  the  species.* 
And  then  in  proof  that  external  causes  initiate  these  pecu- 
liarities, we  have  the  fact  that  in  certain  Daphnidece  "  which 
live  in  places  where  existence  and  parthenogenesis  are  pos- 
sible throughout  the  year,  the  sexual  period  has  disappeared :  " 
there  are  no  males. 

Passing  now  to  animals  which  multiply  by  homogenesis — 
animals  in  which  the  whole  product  of  a  fertilized  germ  ag- 
gregates round  a  single  centre  or  axis  instead  of  round  many 
centres  or  axes — we  see,  as  before,  that  so  long  as  the  con- 
ditions allow  rapid  increase  in  the  mass  of  this  germ-product, 
the  formation  of  new  individuals  by  gamogenesis  does  not 
take  place.  Only  when  growth  is  declining  in  relative  rate, 
do  perfect  sperm-cells  and  germ-cells  begin  to  appear;  and 

*  This  establishment  by  survival  of  the  fittest  of  reproductive  processes 
adapted  to  variable  conditions,  is  indirectly  elucidated  by  the  habits  of 
salmon.  As  salmon  thrive  in  the  sea  and  fall  out  of  condition  in  fresh  water 
(having  during  their  sea-life  not  exercised  the  art  of  catching  fresh-water 
prey),  the  implication  is  that  the  species  would  profit  if  all  individuals  ran  up 
the  rivers  just  before  spawning  time  in  November.  Why  then  do  most  of 
them  run  up  during  many  preceding  months  ?  Contemplation  of  the  difficul- 
ties which  lie  in  the  way  to  the  spawning  grounds,  will,  I  think,  suggest  an 
explanation.  There  are  falls  to  be  leaped  and  shallow  rapids  to  be  ascended. 
These  obstacles  cannot  be  surmounted  when  the  river  is  low.  A  fish  which 
starts  early  in  the  season  has  more  chances  of  getting  up  the  falls  and  the 
rapids  than  one  which  starts  later ;  and,  out  of  condition  as  it  will  be,  may 
spawn,  though  not  well.  On  the  other  hand,  one  which  starts  in  October, 
if  floods  occur  appropriately,  may  reach  the  upper  waters  and  then  spawn  to 
great  advantage ;  but  in  the  absence  of  adequate  rains  it  may  fail  altogether 
to  reach  the  spawning  grounds.  Hence  the  species  profits  by  an  irregularity 
of  habits  adapted  to  meet  irregular  contingencies. 


292  THE  INDUCTIONS  OP  BIOLOGY. 

the  fullest  activity  of  the  reproductive  function  arises  aa 
growth  ceases :  speaking  generally,  at  least ;  for  though  this 
relation  is  tolerably  definite  in  the  highest  orders  of  animals 
which  multiply  by  gamogenesis,  it  is  less  definite  in  the  lower 
orders.  This  admission  does  not  militate  against  the  hypo- 
thesis, as  it  seems  to  do ;  for  the  indefiniteness  of  the  relation 
occurs  where  the  limit  of  growth  is  comparatively  indefinite. 
We  saw  (§46)  that  among  active,  hot-blooded  creatures,  such 
as  mammals  and  birds,  the  inevitable  balancing  of  assimila- 
tion by  expenditure  establishes,  for  each  species,  an  almost 
uniform  adult  size;  and  among  creatures  of  these  kinds 
(birds  especially,  in  which  this  restrictive  effect  of  expendi- 
ture is  most  conspicuous),  the  connexion  between  cessation 
of  growth  and  commencement  of  reproduction  is  distinct. 
But  we  also  saw  (§46)  that  where,  as  in  the  Crocodile  and 
the  Pike,  the  conditions  and  habits  of  life  are  such  that 
expenditure  does  not  overtake  assimilation  as  size  increases, 
there  is  no  precise  limit  of  growth;  and  in  creatures  thus 
circumstanced  we  may  naturally  look  for  a  comparatively 
indeterminate  relation  between  declining  growth  and  com- 
mencing reproduction.*  There  is,  indeed,  among 
fishes,  at  least  one  case  which  appears  very  anomalous.  The 
male  parr,  or  young  of  the  male  salmon,  a  fish  of  four  or  five 
inches  in  length,  is  said  to  produce  milt.  Having,  at  this 
early  stage  of  its  growth,  not  one-hundredth  of  the  weight 
of  a  full-grown  salmon,  how  does  its  production  of  milt 
consist  with  the  alleged  general  law?  The  answer  must  be 
in  great  measure  hypothetical.  If  the  salmon  is  (as  it  ap- 
pears to  be  in  its  young  state)  a  species  of  fresh-water  trout 

*  I  owe  to  Mr.  (now  Sir  John)  Lubbock  an  important  confirmation  of 
this  view.  After  stating  his  belief  that  between  Crustaceans  and  Insects 
there  exists  a  physiological  relation  analogous  to  that  which  exists  between 
water-vertebrata  and  land-vertebrata,  he  pointed  out  to  me  that  while  among 
Insects  there  is  a  definite  limit  of  growth,  and  an  accompanying  definite  com- 
mencement of  reproduction,  among  Crustaceans,  where  growth  has  no  definite 
limit,  there  is  no  definite  relation  between  the  commencement  of  reproduction 
and  the  decrease  or  arrest  of  growth. 


GENESIS.  293 

that  has  contracted  the  habit  of  annually  migrating  to  the 
sea,  where  it  finds  a  food  on  which  it  thrives — if  the  original 
size  of  this  species  was  not  much  greater  than  that  of  the 
parr  (which  is  nearly  as  large  as  some  varieties  of  trout)  — 
and  if  the  limit  of  growth  in  the  trout  tribe  is  very  indefinite, 
as  we  know  it  to  be;  then  we  may  reasonably  infer  that  the 
parr  has  nearly  the  adult  form  and  size  which  this  species 
of  trout  had  before  it  acquired  its  migratory  habit ;  and  that 
this  production  of  milt  is,  in  such  case,  a  concomitant  of  the 
incipient  decline  of  growth  naturally  arising  in  the  species 
when  living  under  the  conditions  of  the  ancestral  species. 
Should  this  be  so,  the  immense  subsequent  growth  of  the 
parr  into  the  salmon,  consequent  on  a  suddenly-increased 
facility  in  obtaining  food,  removes  to  a  great  distance  the 
limit  at  which  assimilation  is  balanced  by  expenditure;  and 
has  the  effect,  analogous  to  that  produced  in  plants,  of  arrest- 
ing the  incipient  reproductive  process.  A  confirmation  of  this 
view  may  be  drawn  from  the  fact  that  when  the  parr,  after 
its  first  migration  to  the  sea,  returns  to  fresh  water,  having 
increased  in  a  few  months  from  a  couple  of  ounces  to  five  or 
six  pounds,  it  no  longer  shows  any  fitness  for  propagation :  the 
grilse,  or  immature  salmon,  does  not  produce  milt  or  spawn. 

We  conclude,  then,  that  the  products  of  a  fertilized  germ  go 
on  accumulating  by  simple  growth,  so  long  as  the  forces 
whence  growth  results  are  greatly  in  excess  of  the  antagonist 
forces;  but  that  when  diminution  of  the  one  set  of  forces 
or  increase  of  the  other,  causes  a  considerable  decline  in 
this  excess  and  an  approach  towards  equilibrium,  fertilized 
germs  are  again  produced.  Whether  the  germ-product  be 
organized  round  one  axis  or  round  the  many  axes  that  arise 
by  agamogenesis,  matters  not.  Whether,  as  in  the  higher 
animals,  this  approach  to  equilibrium  results  from  that  dis- 
proportionate increase'  of  expenditure  entailed  by  increase  of 
size;  or  whether,  as  in  most  plants  and  many  inferior 
animals,  it  results  from  absolute  or  relative  decline  of  nutri- 
tion ;  matters  not.  In  any  case  the  recurrence  of  gamogenesis 


294  THE  INDUCTIONS  OP  BIOLOGY. 

is  associated  with  a  decrease  in  the  excess  of  tissue-producing 
power.  We  cannot  say,  indeed,  that  this  decrease 

always  results  in  gamogenesis:  some  organisms  multiply  for 
an  indefinite  period  by  agamogenesis  only.  The  Weeping 
Willow,  which  has  been  propagated  throughout  Europe,  does 
not  seed  in  Europe;  and  yet,  as  the  Weeping  Willow,  by  its 
large  size  and  the  multiplication  of  generation  upon  genera- 
tion of  lateral  axes,  presents  the  same  causes  of  local  innutri- 
tion as  other  trees,  we  cannot  ascribe  the  absence  of  sexual 
axes  to  the  continued  predominance  of  nutrition.  Among  ani- 
mals, too,  the  anomalous  case  of  the  Tineidce,  a  group  of  moths 
in  which  parthenogenetic  multiplication  goes  on  for  genera- 
tion after  generation,  seems  to  imply  that  gamogenesis  does 
not  necessarily  result  from  an  approximate  balance  of  assimi- 
lation by  expenditure.  What  we  must  say  is  that  an  approach 
towards  equilibrium  between  the  forces  which  cause  growth 
and  the  forces  which  oppose  growth,  is  the  chief  condition  to 
the  recurrence  of  gamogenesis;  but  that  there  appear  to  be 
other  conditions,  in  the  absence  of  which  approach  to  equili- 
brium is  not  followed  by  gamogenesis. 

§,79.  The  above  induction  is  an  approximate  answer  to 
the  question — When  does  gamogenesis  recur?  but  not  to  the 
question  which  was  propounded — Why  does  gamogenesis 
recur  ? — Why  cannot  multiplication  be  carried  on  in  all  cases, 
as  it  is  in  many  cases,  by  agamogenesis?  As  already  said, 
biologic  science  is  not  yet  advanced  enough  to  reply.  Mean- 
while, the  evidence  above  brought  together  suggests  a  certain 
hypothetical  answer. 

Seeing,  on  the  one  hand,  that  gamogenesis  recurs  only  in 
individuals  which  are  approaching  a  state  of  organic  equili- 
brium; and  seeing,  on  the  other  hand,  that  the  sperm-cells 
and  germ-cells  thrown  off  by  such  individuals  are  cells  in 
which  developmental  changes  have  ended  in  quiescence,  but 
in  which,  after  their  union,  there  arises  a  process  of  active 
-  cell-formation ;  we  ma^  suspect"  that  the  approach  towards  a 


GENESIS.  295 

state  of  general  equilibrium  in  such  gamogcnetic  individuals, 
is  accompanied  by  an  approach  towards  molecular  equilibrium 
in  them;  and  that  the  need  for  this  union  of  sperm-cell  and 
germ-cell  is  the  need  for  overthrowing  this  equilibrium,  and 
re-establishing  active  molecular  change  in  the  detached  germ 
— a  result  probably  effected  by  mixing  the  slightly  different 
physiological  units  of  slightly  different  individuals.  The 
several  arguments  which  support  this  view,  cannot  be  satis- 
factorily set  forth  until  after  the  topics  of  Heredity  and 
Variation  have  been  dealt  with.  Leaving  it  for  the  present, 
I  propose  hereafter  to  re-consider  it  in  connexion  with  sundry 
others  raised  by  the  phenomena  of  Genesis. 

But  before  ending  the  chapter,  it  may  be  well  to  note  the 
relations  between  these  different  modes  of  multiplication,  and 
the  conditions  of  existence  under  which  they  are  respectively 
habitual.  While  the  explanation  of  the  teleologist  is  untru-e, 
it  is  often  an  obverse  to  the  truth;  for  though,  on  the  hypo- 
thesis of  Evolution,  it  is  clear  that  things  are  not  arranged 
thus  or  thus  for  the  securing  of  special  ends,  it -is  also  clear 
that  arrangements  which  do  secure  these  special  ends  tend 
to  establish  themselves — are  established  by  their  fulfilment 
of  these  ends.  Besides  insuring  a  structural  fitness  between 
each  kind  of  organism  and  its  circumstances,  the  working 
of  "  natural  selection  "  also  insures  a  fitness  between  the  mode 
and  rate  of  multiplication  of  each  kind  of  organism  and 
its  circumstances.  We  may,  therefore,  without  any  teleo- 
logical  implication,  consider  the  fitness  of  homogenesis  and 
heterogenesis  to  the  needs  of  the  different  classes  of  organisms 
which  exhibit  them. 

Heterogenesis  prevails  among  organisms  of  which  the  food, 
though  abundant  compared  with  their  expenditure,  is  dis- 
persed in  such  a  way  that  it  cannot  be  appropriated  in  a 
wholesale  manner.  Protophyta,  subsisting  on  diffused  gases 
and  decaying  organic  matter  in  a  state  of  minute  subdivision, 
and  Protozoa,  to  which  food  comes  in  the  shape  of  extremely 
small  floating  particles,  are  enabled,  by  their  rapid  agamo- 


290  THE  INDUCTIONS  OF  BIOLOGY. 

genetic  multiplication,  to  obtain  materials  for  growth  better 
than  they  would  do  did  they  not  thus  continually  divide  and 
disperse  in  pursuit  of  it.  The  higher  plants,  having  for 
nutriment  the  carbonic  acid  of  the  air  and  certain  mineral 
components  of  the  soil,  show  us  modes  of  multiplication 
adapted  to  the  fullest  utilization  of  these  substances.  A 
herb  with  but  little  power  of  forming  the  woody  fibre  re- 
quisite to  make  a  stem  that  can  support  wide-spreading 
branches,  after  producing  a  few  sexless  axes  produces  sexual 
ones;  and  maintains  its  race  better,  by  the  consequent  early 
dispersion  of  seeds,  than  by  a  further  production  of  sexless 
axes.  But  a  tree,  able  to  lift  its  successive  generations  of 
sexless  axes  high  into  the  air,  where  each  gets  carbonic  acid 
and  light  almost  as  freely  as  if  it  grew  by  itself,  may  with 
advantage  go  on  budding-out  sexless  axes  year  after  year; 
since  it  thereby  increases  its  subsequent  power  of  budding- 
out  sexual  axes.  Meanwhile  it  may  advantageously  trans- 
form into  seed-bearers  those  axes  which,  in  consequence  of 
their  less  direct  access  to  materials  absorbed  by  the  roots, 
are  failing  in  their  nutrition ;  for  it  thus  throws  off  from  a 
point  at  which  sustenance  is  deficient,  a  migrating  group  of 
germs  that  may  find  sustenance  elsewhere.  The  hetero- 
genesis  displayed  by  animals  of  the  Coelenterate  type  has 
evidently  a  like  utility.  A  polype,  feeding  on  minute 
annelids  and  crustaceans  which,  flitting  through  the  water, 
come  in  contact  with  its  tentacles,  and  limited  to  that  quan- 
tity of  prey  which  chance  brings  within  its  grasp,  buds  out 
young  polypes  which,  either  as  a  colony  or  as  dispersed  in- 
dividuals, spread  their  tentacles  through  a  larger  space  of 
water  than  the  parent  alone  can;  and  by  producing  them, 
the  parent  better  insures  the  continuance  of  its  species  than 
it  would  do  if  it  went  on  slowly  growing  until  its  nutrition 
was  nearly  balanced  by  its  waste,  and  then  multiplied  by 
gamogenesis.  Similarly  with  the  Aphis.  Living  on  sap 
sucked  from  tender  shoots  and  leaves,  and  able  thus  to  take 
in  but  a  very  small  quantity  in  a  given  time,  this  creature's 


GENESIS.  297 

race  is  more  likely  to  be  preserved  by  a  rapid  asexual  pro- 
pagation of  small  individuals,  which  disperse  themselves  over 
a  wide  area  of  nutrition,  than  it  would  be  did  the  indi- 
vidual growth  continue  so  as  to  produce  large  individuals 
multiplying  sexually.  And  then  when  autumnal  cold  and 
diminishing  supply  of  sap  put  a  check  to  growth,  the  recur- 
rence of  gamogenesis,  or  production  of  fertilized  ova  which 
remain  dormant  through  the  winter,  is  more  favourable  to 
the  preservation  of  the  race  than  would  be  a  further  con- 
tinuance of  agamogenesis.  On  the  other  hand,  among 
the  higher  animals  living  on  food  which,  though  dispersed, 
is  more  or  less  aggregated  into  large  masses,  this  alternation 
of  gamic  and  agamic  reproduction  ceases  to  be  useful.  The 
development  of  the  germ-product  into  a  single  organism  of 
considerable  bulk,  is  in  many  cases  a  condition  without 
which  these  large  masses  of  nutriment  could  not  be  appro- 
priated; and  here  the  formation  of  many  individuals  instead 
of  one  would  be  fatal.  But  we  still  see  the  beneficial  results 
of  the  general  law — the  postponement  of  gamogenesis  until 
the  rate  of  growth  begins  to  decline.  For  so  long  as  the  rate 
of  growth  continues  rapid,  there  is  proof  that  the  organism 
gets  food  with  facility — that  expenditure  does  not  seriously 
check  accumulation;  and  that  the  size  reached  is  as  yet  not 
disadvantageous :  or  rather,  indeed,  that  it  is  advantageous. 
But  when  the  rate  of  growth  is  much  decreased  by  the 
increase  of  expenditure — when  the  excess  of  assimilative 
power  is  diminishing  so  fast  as  to  indicate  its  approaching 
disappearance — it  becomes  needful,  for  the  maintenance  of 
the  species,  that  this  excess  shall  be  turned  to  the  production 
of  new  individuals;  since,  did  growth  continue  until  there 
was  a  complete  balancing  of  assimilation  and  expenditure, 
the  production  of  new  individuals  would  be  either  impossible 
or  fatal  to  the  parent.  And  it  is  clear  that  "  natural  selec- 
tion "  will  continually  tend  to  determine  the  period  at  which 
gamogenesis  commences,  in  such  a  way  as  most  favours  the 
maintenance  of  the  race. 


298  THE  INDUCTIONS  OF  BIOLOGY. 

Here,  too,  may  fitly  >be  pointed  out  the  fact  that,  by 
"  natural  selection,"  there  will  in  every  case  be  produced  the 
most  advantageous  proportion  of  males  and  females.  If  the 
conditions  of  life  render  numerical  inequality  of  the  sexes 
beneficial  to  the  species,  in  respect  either  of  the  number  of 
the  offspring  or  the  character  of  the  offspring;  then,  those 
varieties  of  the  species  which  approach  more  than  other 
varieties  towards  this  beneficial  degree  of  inequality,  will  be 
apt  to  supplant  other  varieties.  And  conversely,  where 
equality  in  the  number  of  males  and  females  is  beneficial, 
the  equilibrium  will  be  maintained  by  the  dying  out  of  such 
varieties  as  produce  offspring  among  which  the  sexes  are  not 
balanced. 

NOTE. — Such  alterations  of  statement  in  this  chapter  as 
have  been  made  necessary  by  the  advance  of  biological  know- 
ledge since  1864  have  not,  I  think,  tended  to  invalidate  its 
main  theses,  but  have  tended  to  verify  them.  Some  expla- 
nations to  be  here  added  may  remove  remaining  difficulties. 

Certain  types,  which  are  transitional  between  Protozoa  and 
Metazoa,  exhibit  under  its  simplest  form  the  relation  between 
self-maintenance  and  race-maintenance — the  integration 
primarily  effecting  the  one  and  the  disintegration  primarily 
effecting  the  other.  Among  the  Myceiozoa  a  number  of 
amceba-like  individuals  aggregate  into  what  is  called  a 
plasmodium;  and  while,  in  some  orders,  they  become  fused 
into  a  mass  of  protoplasm  through  which  their  nuclei  are 
dispersed,  in  other  orders  (Sorophora)  they  retain  their  indi- 
vidualities and  simply  form  a  coherent  aggregate.  These 
last,  presumably  the  earliest  in  order  of  evolution,  remain 
united  so  long  as  the  plasmodium,  having  a  small  power  of 
locomotion,  furthers  the  general  nutrition;  but  when  this 
is  impeded  by  drought  or  cold,  there  arise  spores.  Eich 
spore  contains  an  amoeboid  individual;  and  this,  escaping 
when  favourable  conditions  return,  establishes  by  fission  and 
by  union  with  others  like  itself  a  new  colony  or  plasmodium. 


GENESIS.  299 

Reduced  to  its  lowest  terms,  we  here  see  the  antagonism 
between  that  growth  of  the  coherent  mass  of  units  which 
accompanies  its  physical  prosperity,  and  that  incoherence  and 
dispersion  of  the  units  which  follows  unfavourable  condi- 
tions and  arrest  of  growth,  and  which  presently  initiates  new 
plasmodia. 

This  antagonism,  seen  in  these  incipient  Metazoa  which 
show  us  none  of  that  organization  characterizing  the  Metazoa 
in  general,  is  everywhere  in  more  or  less  disguised  forms 
exhibited  by  them — must  necessarily  be  so  if  growth  of  the 
individual  is  a  process  of  integration  while  formation  of  new 
individuals  is  a  process  of  disintegration.  And,  primarily,  it 
is  an  implication  that  whatever  furthers  the  one  impedes  the 
other. 

But  now  while  recognizing  the  truth  that  nutrition  and 
innutrition  (using  these  words  to  cover  not  supply  of  nutri- 
ment only  but  the  presence  of  other  influences  favourable  or 
unfavourable  to  the  vital  processes)  primarily  determine  the 
alternations  of  these;  we  have  also  to  recognize  the  truth 
that  from  the  beginning  survival  of  the  fittest  has  been 
shaping  the  forms  and  effects  of  their  antagonism.  By  in- 
heritance a  physiological  habit  which  modifies  the  form  of 
the  antagonism  in  a  way  favourable  to  the  species,  will  become 
established.  Especially  will  this  be  the  case  where  the  lives 
of  the  individuals  have  become  relatively  definite  and  where 
special  organs  have  been  evolved  for  casting  off  reproductive 
centres.  The  resulting  physiological  rhythm  may  in  such 
cases  become  so  pronounced  as  greatly  to  obscure  the  primi- 
tive relation.  Among  plants  we  see  this  in  the  fact  that 
those  which  have  been  transferred  from  one  habitat  to  another 
having  widely  different  seasons,  long  continue  their  original 
time  of  flowering,  though  it  is  inappropriate  to  the  new  cir- 
cumstances— the  reproductive  periodicity  has  become  organic. 
Similarly  in  each  species  of  higher  animal,  development  of 
the  reproductive  organs  and  maturation  of  reproductive 
cells  take  place  at  a  settled  age,  whether  the  conditions  have 


300  THE  INDUCTIONS  OF  BIOLOGY. 

been  favourable  or  unfavourable  to  physical  prosperity.  The 
established  constitutional  tendency,  adapted  to  the  needs  of 
the  species,  over-rides  the  constitutional  needs  of  the  indi- 
vidual. 

Even  here,  however,  the  primitive  antagonism,  though 
greatly  obscured,  occasionally  shows  itself.  Instance  the 
fact  that  in  plants  where  gamogenesis  is  commencing  a  sudden 
access  of  nutrition  will  cause  resumption  of  agamogenesis ; 
and  I  suspect  that  an  illustration  may  be  found  among 
human  beings  in  the  earlier  establishment  of  the  reproduc- 
tive function  among  the  ill-fed  poor  than  among  the  well-fed 
rich. 

One  other  qualification  has  to  be  added.  In  plants  and 
animals  which  have  become  so  definitely  constituted  that  at 
an  approximately  fixed  stage,  the  proclivity  towards  the  pro- 
duction of  new  individuals  becomes  pronounced,  it  naturally 
happens  that  good  nutrition  aids  it.  Surplus  nutriment  being 
turned  into  the  reproductive  channel,  the  reproduction  is 
efficient  in  proportion  as  the  surplus  is  great.  Hence  the 
fact  that  in  fruit  trees  which  have  reached  the  flowering  stage, 
manuring  has  the  effect  that  though  it  does  not  increase  the 
quantity  of  blossoms  it  increases  the  quantity  of  fruit;  and 
hence  the  fact  that  well-fed  and  easy-living  races  of  men  are 
prolific. 


CHAPTER  VIII. 

HEREDITY. 

§  80.  ALREADY,  in  the  last  two  chapters,  the  law  of  heredi- 
tary transmission  has  been  tacitly  assumed;  as,  indeed,  it 
unavoidably  is  in  all  such  discussions.  Understood  in  its 
entirety,  the  law  is  that  each  plant  or  animal,  if  it  repro- 
duces, gives  origin  to  others  like  itself:  the  likeness  consist- 
ing, not  so  much  in  the  repetition  of  individual  traits  as  in  the 
assumption  of  the  same  general  structure.  This  truth  has 
been  rendered  so  familiar  by  daily  illustration  as  almost  to 
have  lost  its  significance.  ^  That  wheat  produces  wheat — that 
existing  oxen  have  descended  from  ancestral  oxen — that  every 
unfolding  organism  eventually  takes  the  form  of  the  class, 
order,  genus,  and  species  from  which  it  sprang;  is  a  fact 
which,  by  force  of  repetition,  has  acquired  in  our  mind.j 
almost  the  aspect  of  a  necessity.  It  is  in  this,  however, 
that  Heredity  is  principally  displa}Ted:  the  manifestations  of 
it  commonly  referred  to  being  quite  subordinate.  And,  as 
thus  understood,  Heredity  is  universal.  The  various  instances 
of  heterogenesis  lately  contemplated  seem,  indeed,  to  be  at 
variance  with  this  assertion.  But  they  are  not  really  so. 
Though  the  recurrence  of  like  forms  is,  in  these  instance.-;, 
not  direct  but  cyclical,  still,  the  like  forms  do  recur;  and, 
when  taken  together,  the  group  of  forms  produced  during  one 
of  the  cycles  is  as  much  like  the  groups  produced  in  pre- 
ceding cycles,  as  the  single  individual  arising  by  homo- 
genesis  is  like  ancestral  individuals. 

801 


302  THE  INDUCTIONS  OP  BIOLOGY. 

While,  however,  the  general  truth  that  organisms  of  a 
given  type  uniformly  descend  from  organisms  of  the  same 
type,  is  so  well  established  by  infinite  illustrations  as  to  have 
assumed  the  character  of  an  axiom;  it  is  not  universally 
admitted  that  non-typical  peculiarities  are  inherited.  Many 
entertain  a  vague  belief  that  the  law  of  Heredity  applies 
only  to  main  characters  of  structure  and  not  to  details; 
or,  at  any  rate,  that  though  it  applies  to\§uch  details  as 
constitute  differences  of  species,  it  does  not  apply  to  smaller 
details.  The  circumstance  that  the  tendency  to  repetition 
is  in  a  slight  degree  qualified  by  the  tendency  to  variation 
(which,  as  we  shall  hereafter  see,  is  but  an  indirect  result 
of  the  tendency  to  repetition),  leads  some  to  doubt  whether 
Heredity  is  unlimited.  A  careful  weighing  of  the  evidence, 
however,  and  a  due  allowance  for  the  influences  by  which  the 
minuter  manifestations  of  Heredity  are  obscured,  may  remove 
this  scepticism. 

First  in  order  of  importance  comes  the  fact  that  not  only 
are  there  uniformly  transmitted  from  an  organism  to  its  off- 
spring, those  traits  of  structure  which  distinguish  the  class, 
order,  genus,  and  species;  but  also  those  which  distinguish 
the  variety.  We  have  numerous  cases,  among  both  plants 
and  animals,  where,  by  natural  or  artificial  conditions,  there 
have  been  produced  divergent  modifications  of  the  same 
species;  and  abundant  proof  exists  that  the  members  of  any 
one  sub-species  habitually  transmit  their  distinctive  pecu- 
liarities to  their  descendants.  Agriculturists  and 
gardeners  can  furnish  unquestionable  illustrations.  Several 
varieties  of  wheat  are  known,  of  which  each  reproduces  itself. 
Since  the  potato  was  introduced  into  England  there  have 
been  formed  from  it  a  number  of  sub-species;  some  of  them 
differing  greatly  in  their  forms,  sizes,  qualities,  and  periods 
of  ripening.  Of  peas,  also,  the  like  may  be  said.  And  the 
case  of  the  cabbage-tribe  is  often  cited  as  showing  the  per- 
manent establishment  of  races  which  have  diverged  widely 
from  a  common  stock.  Among  fruits  and  flowers  the  multi- 


HEREDITY.  303 

plication  of  kinds,  and  the  continuance  of  each  kind  with 
certainty  by  agamogenesis,  and  to  some  extent  by  gamo- 
genesis,  might  be  exemplified  without  end.  From  all 

sides  evidence  may  be  gathered  showing  a  like  persistence  of 
varieties  among  animals.  We  have  our  distinct  breeds  of 
sheep,  our  distinct  breeds  of  cattle,  our  distinct  breeds  of 
horses:  each  breed  maintaining  its  characteristics.  The 
many  sorts  of  dogs  which,  if  we  accept  the  physiological 
test,  we  must  consider  as  all  of  one  species,  show  us  in  a 
marked  manner  the  hereditary  transmission  of  small  differ- 
ences— each  sort,  when  kept  pure,  reproducing  itself  not  only 
in  size,  form,  colour,  and  quality  of  hair,  but  also  in  disposi- 
tion and  speciality  of  intelligence.  Poultry,  too,  have  their 
permanently-established  races.  And  the  Isle  of  Man  sends 
us  a  tail-less  kind  of  cat.  Even  in  the  absence  of 

other  evidence,  that  which  ethnology  furnishes  would  suffice. 
Grant  them  to  be  derived  from  one  stock,  and  the  varieties 
of  man  yield  proof  upon  proof  that  non-specific  traits  of 
structure  are  bequeathed  from  generation  to  generation.  Or 
grant  onl^  their  derivation  from  several  stocks,  and  we  still 
have,  between  races  descended  from  a  common  stock,  dis- 
tinctions which  prove  the  inheritance  of  minor  peculiarities. 
Besides  seeing  the  Negroes  continue  to  produce  Negroes, 
copper-coloured  men  to  produce  men  of  a  copper  colour,  and 
the  fair-skinned  races  to  perpetuate  their  fair  skins — besides 
seeing  that  the  broad-faced  and  flat-nosed  Calmuck  begets 
children  with  broad  faces  and  flat  noses,  while  the  Jew 
bequeaths  to  his  offspring  the  features  which  have  so  long 
characterized  Jews;  we  see  that  those  small  unlikenesses 
which  distinguish  more  nearly-allied  varieties  of  men,  are 
maintained  from  generation  to  generation.  In  Germany,  the 
ordinary  shape  of  skull  is  appreciably  different  from  that 
common  in  Britain:  near  akin  though  the  Germans  are  to 
the  British.  The  average  Italian  face  continues  to  be  unlike 
the  faces  of  northern  nations.  The  French  character  is  now, 
as  it  was  centuries  ago,  contrasted  in  sundry  respects  with 


304  THE  INDUCTIONS  OF  BIOLOGY. 

the  characters  of  neighbouring  peoples.  Nay,  even  between 
races  so  closely  allied  as  the  Scotch  Celts,  the  Welsh  Celts, 
and  the  Irish  Celts,  appreciable  differences  of  form  and  nature 
have  become  established. 

The  fact  that  sub-species  and  sub-sub-species  thus  exem- 
plify the  general  law  of  inheritance  which  shows  itself  in  the 
perpetuation  of  ordinal,  generic,  and  speciiX  peculiarities,  is 
strong  reason  for  the  belief  that  this  general  lay  is  unlimited 
in  its  application.  This  has  the  support  of  still  more  special 
evidences.  They  are  divisible  into  two  classes.  In  the  one 
come  cases  where  congenital  peculiarities,  not  traceable  to 
any  obvious  causes,  are  bequeathed  to  descendants.  In  the 
other  come  cases  where  the  peculiarities  thus  bequeathed  are 
not  congenital,  but  have  resulted  from  changes  of  functions 
during  the  lives  of  the  individuals  bequeathing  them.  We 
will  consider  first  the  cases  that  come  in  the  first  class. 

§  81.  Note  at  the  outset  the  character  of  the  chief  testi- 
mony. Excluding  those  inductions  that  have  been  so  fully 
verified  as  to  rank  with  exact  science,  there  are  no  inductions 
so  trustworthy  as  those  which  have  undergone  the  mercantile 
test.  When  we  have  thousands  of  men  whose  profit  or  loss 
depends  on  the  truth  of  their  inferences  from  perpetually- 
repeated  observations ;  and  when  we  find  that  their  inferences, 
handed  down  from  generation  to  generation,  have  generated  an 
unshakable  conviction;  we  may  accept  it  without  hesitation. 
In  breeders  of  animals  we  have  such  a  class,  led  by  such 
experiences,  and  entertaining  such  a  conviction — the  convic- 
tion that  minor  peculiarities  of  organization  are  inherited  as 
well  as  major  peculiarities.  Hence  the  immense  prices  given 
for  successful  racers,  bulls  of  superior  forms,  sheep  that  have 
certain  desired  peculiarities.  Hence  the  careful  record  of 
pedigrees  of  high-bred  horses  and  sporting  dogs.  Hence  the 
care  taken  to  avoid  intermixture  with  inferior  stocks.  A  ; 
quoted  by  Mr.  Darwin,  Youatt  says  the  principle  of  selection 
"enables  the  agriculturist  not  only  to  modify  the  character 


HEREDITY.  305 

of  his  flock  but  to  change  it  altogether."  Lord  Somerville, 
speaking  of  what  breeders  have  done  for  sheep,  says : — "  It 
would  seem  that  the}r  have  chalked  upon  a  wall  a  form  per- 
fect in  itself  and  then  given  it  existence."  That  most  skil- 
ful breeder,  Sir  John  Sebright,  used  to  say,  with  respect  to 
pigeons,  that  "  he  would  produce  any  given  feather  in  three 
years,  but  it  would  take  him  six  years  to  obtain  head  and 
beak."  In  all  which  statements  the  tacit  assertion  is,  that 
individual  traits  are  bequeathed  from  generation  to  genera- 
tion, and  may  be  so  perpetuated  and  increased  as  to  become 
permanent  distinctions. 

Of  special  instances  there  are  many  besides  that  of  the 
often-cited  Otto-breed  of  sheep,  descended  from  a  single  ehort- 
legged  lamb,  and  that  of  the  six-fingered  Gratio  Kelleia,  who 
transmitted  his  peculiarity,  in  different  degrees,  to  several  of 
his  children  and  to  some  of  his  grandchildren.  In  a  paper 
contributed  to  the  Edinburgh  New  Philosophical  Journal  for 
July,  18G3,  Dr.  (now  Sir  John)  Struthers  gives  cases  of  heredi- 
tary digital  variations.  Esther  P — ,who  had  six  fingers  on  one 
hand.,  bequeathed  this  malformation  along  some  lines  of  her 
descendants  for  two,  three,  and  four  generations.  A —  S — 
inherited  an  extra  digit  on  each  hand  and  each  foot  from  his 
father;  and  C —  G — ,  who  also  had  six  fingers  and  six  toes, 
had  an  aunt  and  a  grandmother  similarly  formed.  A  collec- 
tion of  evidence  published  by  Mr.  Sedgwick  in  the  Medico- 
Chirurgical  Review  for  April  and  for  July,  1863,  in  two 
articles  on  "  The  Influence  of  Sex  in  limiting  Hereditary 
Transmission/'  includes  the  following  cases : — Augustin 
Duforet,  a  pastry-cook  of  Douai,  who  had  but  two  instead  of 
three  phalanges  to  all  his  fingers  and  toes,  inherited  this 
malformation  from  his  grandfather  and  father,  and  had  it  in 
common  with  an  uncle  and  numerous  cousins.  An  account 
has  been  given  by  Dr.  Lepine,  of  a  man  with  only  three 
fingers  on  each  hand  and  four  toes  on  each  foot,  and  whose 
rrandfather  and  son  exhibited  the  like  anomaly.  Bechet 
describes  Victoire  Barre  as  a  woman  who,  like  her  father  and 


306  THE   INDUCTIONS  OP  BIOLOGY. 

sister,  had  but  one  developed  finger  on  each  hand  and  but 
two  toes  on  each  foot,  and  whose  monstrosity  re-appeared  in 
two  daughters.  And  there  is  a  case  where  the  absence  of 
two  distal  phalanges  on  the  hands  was  traced  for  two  genera- 
tions. The  various  recorded  instances  in  which  there  has 
been  transmission  from  one  generation  to  another,  of  webbed- 
fingers,  of  webbed-toes,  of  hare-lip,  of  congenital  luxation  of 
the  thigh,  of  absent  patellae,  of  club-foot,  &c.,  would  occupy 
more  space  than  can  here  be  spared.  Defects  in  the 

organs  of  sense  are  also  not  unfrequently  inherited.  Four 
sisters,  their  mother,  and  grandmother,  are  described  by 
Duval  as  similarly  affected  by  cataract.  Prosper  Lucas 
details  an  example  of  amaurosis  affecting  the  females  of  a 
family  for  three  generations.  Duval,  Graffe,  Dufon,  and 
others  testify  to  like  cases  coming  under  their  observation.* 
Deafness,  too,  is  occasionally  transmitted  from  parent  to  child. 
There  are  deaf-mutes  whose  imperfections  have  been  derived 
from  ancestors;  and  malformations  of  the  external  ears  have 
also  been  perpetuated  in  offspring.  Of  transmitted 

peculiarities  of  the  skin  and  its  appendages,  many  cases  have 
been  noted.  One  is  that  of  a  family  remarkable  for  enorm- 
ous black  eyebrows;  another  that  of  a  family  in  which 
every  member  had  a  lock  of  hair  of  a  lighter  colour  than  the 
rest  on  the  top  of  the  head;  and  there  are  also  instances  of 
congenital  baldness  being  hereditary.  From  one  of  our  lead- 
ing sculptors  I  learn  'that  his  wife  has  a  flat  mole  under 
the  foot  near  the  little  toe,  and  one  of  her  sons  has  the  same. 
Entire  absence  of  teeth,  absence  of  particular  teeth,  and 
anomalous  arrangements  of  teeth,  are  recorded  as  traits  that 
have  descended  to  children.  And  we  have  evidence  that  sound- 
ness and  unsoundness  of  teeth  are  transmissible. 

The  inheritance  of  tendencies  to  such  diseases  as  gout, 

*  While  this  chapter  is  passing  through  the  press,  I  learn  from  Mr.  White 
Cooper,  that  not  only  are  near  sight,  long  sight,  dull  sight,  and  squinting, 
hereditary ;  but  that  a  peculiarity  of  vision  confined  to  one  eye  is  frequently 
transmitted  :  re-appearing  in  the  same  eye  in  offspring. 


HEREDITY.  .  307 

consumption,  and  insanity  is  universally  admitted.  Among 
the  less-common  diseases  of  which  the  descent  has  been  ob- 
served, are  ichthyosis,  leprosy,  pityriasis,  sebaceous  tumours, 
plica  polonica,  dipsomania,  somnambulism,  catalepsy,  epi- 
lepsy, asthma,  apoplexy,  elephantiasis.  General  nervousness 
displayed  by  parents  almost  always  re-appears  in  their  chil- 
dren. Even  a  bias  towards  suicide  appears  to  be  sometimes 
hereditary. 

§  82.  To  prove  the  transmission  of  those  structural  pecu- 
liarities which  have  resulted  from  functional  peculiarities,  is, 
for  several  reasons,  comparatively  difficult.  Changes  pro- 
duced in  the  sizes  of  parts  fay  changes  in  their  amounts  of 
action,  are  mostly  unobtrusive.  A  muscle  which  has  increased 
in  bulk  is  usually  so  obscured  by  natural  or  artificial  cloth- 
ing, that  unless  the  alteration  is  extreme  it  passes  without 
remark.  Such  nervous  developments  as  are  possible  in  the 
course  of  a  single  life,  cannot  be  seen  externally.  Visceral 
modifications  of  a  normal  kind  are  observable  but  obscurely, 
or  not  at  all.  And  if  the  changes  of  structure  worked  in 
individuals  by  changes  in  their  habits  are  thus  difficult  to 
trace,  still  more  difficult  to  trace  must  be  the  transmission  of 
them:  further  hidden,  as  this  is,  by  the  influences  of  other 
individuals  who  are  often  otherwise  modified  by  other 
habits.  Moreover,  such  specialities  of  structure  as  are  due 
to  specialities  of  function,  are  usually  entangled  with  speciali- 
ties of  structure  which  are,  or  may  be,  due  to  selection,  natural 
or  artificial.  In  most  cases  it  is  impossible  to  say  that  a 
structural  peculiarity  which  seems  to  have  arisen  in  offspring 
from  a  functional  peculiarity  in  a  parent,  is  wholly  inde- 
pendent of  some  congenital  peculiarity  of  structure  in  the 
parent,  whence  this  functional  peculiarity  arose.  We  are 
restricted  to  cases  with  which  natural  or  artificial  selection 
can  have  had  nothing  to  do,  and  such  cases  are  difficult  to 
find.  Some,  however,  may  be  noted. 

A  species  of  plant  that  has  been  transferred  from  one  soil 


308  THE  INDUCTIONS  OF  BIOLOGY. 

or  climate  to  another,  frequently  undergoes  what  botanists 
call  "  change  of  habit " — a  change  which,  without  affecting 
its  specific  characters,  is  yet  conspicuous.  In  its  new  locality 
the  species  is  distinguished  by  leaves  that  are  much  larger 
or  much  smaller,  or  differently  shaped,  or  more  fleshy;  or 
instead  of  being  as  before  comparatively  smooth,  it  becomes 
hairy ;  or  its  stem  becomes  woody  instead  of  being  herbaceous ; 
or  its  branches,  no  longer  growing  upwards,  assume  a  droop- 
ing character.  Now  these  "  changes  of  habit "  are  clearly 
determined  by  functional  changes.  Occurring,  as  they  do,  in 
many  individuals  which  have  undergone  the  same  transporta- 
tion, they  cannot  be  classed  as  "  spontaneous  variations/' 
They  are  modifications  of  structure  consequent  on  modifica- 
tions of  function  that  have  been  produced  by  modifications 
in  the  actions  of  external  forces.  And  as  these  modifications 
re-appear  in  succeeding  generations,  we  have,  in  them,  ex- 
amples of  functionally-established  variations  that  are  here- 
ditarily transmitted. 

Evidence  of  analogous  changes  in  animals  is  difficult  to 
disentangle.  Only  among  domesticated  kinds  have  we  any 
opportunity  of  tracing  the  results  of  altered  habits ;  and  here, 
in  nearly  all  cases,  artificial  selection  has  obscured  them. 
Still,  there  are  some  facts  which  seem  to  the  point.  Mr. 
Darwin,  while  ascribing  almost  wholly  to  "  natural  selection  " 
the  production  of  those  modifications  which  eventuate  in 
differences  of  species,  nevertheless  admits  the  effects  of  use 
and  disuse.  He  says — "  I  find  in  the  domestic  duck  that  the 
bones  of  the  wing  weigh  less  and  the  bones  of  the  leg  more, 
in  proportion  to  the  whole  skeleton,  than  do  the  same  bones 
in  the  wild  duck;  and  I  presume  that  this  change  may  be 
safely  attributed  to  the  domestic  duck  flying  much  less,  and 
walking  more,  than  its  wild  parent.  The  great  and  inherited 
development  of  the  udders  in  cows  and  goats  in  countries 
where  they  are  habitually  milked,  in  comparison  with  the 
state  of  these  organs  in  other  countries,  is  another  instance  of 
the  effect  of  use.  Not  a  single  domestic  animal  can  be  named 


HEREDITY.  309 

which  has  not  in  some  country  drooping  ears;  and  the  view 
suggested  by  some  authors,  that  the  drooping  is  due  to  the 
disuse  of  the  muscles  of  the  ear,  from  the  animals  not  being 
much  alarmed  by  danger,  seems  probable."  Again — "  The 
eyes  of  moles  and  of  some  burrowing  rodents  are  rudimentary 
in  size,  and  in  some  cases  are  quite  covered  up  by  skin  and 
fur.  This  state  of  the  eyes  is  probably  due  to  gradual 
reduction  from  disuse,  but  aided  perhaps  by  natural  selec- 
tion." .  .  .  .  "  It  is  well  known  that  several  animals 
belonging  to  the  most  different  classes,  which  inhabit  the 
caves  of  Styria  and  of  Kentucky,  are  blind.  In  some  of  the 
crabs  the  footstalk  of  the  eye  remains,  though  the  eye  is 
gone;  the  stand  for  the  telescope  is  there,  though  the  tele- 
scope with  its  glasses  has  been  lost.  As  it  is  difficult  to 
imagine  that  eyes,  though  useless,  could  be  in  any  way 
injurious  to  animals  living  in  darkness,  I  attribute 
their  loss  wholly  to  disuse."  *  The  direct  inheritance  of  an 
acquired  peculiarity  is  sometimes  observable.  Mr.  Lewes 
gives  a  case.  He  "had  a  puppy  taken  from  its  mother  at 
six  weeks  old,  who,  although  never  taught  'to  beg'  (an 
accomplishment  his  mother  had  been  taught),  spontaneously 
took  to  begging  for  everything  he  wanted  when  about  seven 
or  eight  months  old:  he  would  beg  for  food,  beg  to  be  let 
out  of  the  room,  and  one  day  was  found  opposite  a  rabbit 
hutch  begging  for  rabbits."  Instances  are  on  record,  too,  of 

*  An  instance  here  occurs  of  the  way  in  which  those  who  are  averse  to  a 
conclusion  will  assign  the  most  flimsy  reasons  for  rejecting  it.  Rather  than 
admit  that  the  eyes  of  these  creatures  living  in  darkness  have  disappeared 
from  lack  of  use,  some  contend  that  such  creatures  would  be  liable  to  have 
their  eyes  injured  by  collisions  with  objects,  and  that  therefore  natural  selec- 
tion would  favour  those  individuals  in  which  the  eyes  had  somewhat  dimin- 
ished and  were  least  liable  to  injury :  the  implication  being  that  the  immunity 
from  the  inflammations  due  to  injuries  would  be  so  important  a  factor  in  life 
as  to  cause  survival.  And  this  is  argued  in  presence  of  the  fact  that  one  of 
the  most  conspicuous  among  these  blind  cave-animals  is  a  cray-fish,  and  that 
the  cray-fish  in  its  natural  habitat  is  in  the  habit  of  burrowing  in  the  banks 
of  rivers  holes  a  foot  or  more  deep,  and  has  its  eyes  exposed  to  all  those 
possible  blows  and  frictions  which  the  burrowing  involves ! 
21 


310  THE  INDUCTIONS  OF  BIOLOGY. 

sporting  dogs  which  spontaneously  adopted  in  the  field,  certain 
modes  of  behaviour  which  their  parents  had  learnt. 

But  the  best  examples  of  inherited  modifications  produced 
by  modifications  of  function,  occur  in  mankind.  To  no 
other  cause  can  be  ascribed  the  rapid  metamorphoses  under- 
gone by  the  British  races  when  placed  in  new  conditions. 
In  the  United  States  the  descendants  of  the  immigrant  Irish 
lose  their  Celtic  aspect,  and  become  Americanized.  This 
cannot  be  ascribed  to  mixture,  since  the  feeling  with  which 
Irish  are  regarded  by  Americans  prevents  any  considerable 
amount  of  intermarriage.  Equally  marked  is  the  case  of  the 
immigrant  Germans  who,  though  they  keep  very  much  apart, 
rapidly  assume  the  prevailing  type.  To  say  that  "spon- 
taneous variation"  increased  by  natural  selection,  can  have 
produced  this  effect,  is  going  too  far.  Peoples  so  numerous 
cannot  have  been  supplanted  in  the  course  of  two  or  three 
generations  by  varieties  springing  from  them.  Hence  the 
implication  is  that  physical  and  social  conditions  have 
wrought  modifications  of  function  and  structure,  which  off- 
spring have  inherited  and  increased.  Similarly  with  special 
cases.  In  the  Cyclopcedia  of  Practical  Medicine,  Vol.  II.,  p. 
419,  Dr.  Brown  states  that  he  "  has  in  many  instances  ob- 
served in  the  case  of  individuals  whose  complexion  and 
general  appearance  has  been  modified  by  residence  in  hot 
climates,  that  children  born  to  them  subsequently  to  such 
residence,  have  resembled  them  rather  in  their  acquired  than 
primary  mien." 

Some  visible  modifications  of  organs  caused  by  changes  in 
their  functions,  may  be  noted.  That  large  hands  are  inherited 
by  those  whose  ancestors  led  laborious  lives,  and  that  those 
descended  from  ancestors  unused  to  manual  labour  com- 
monly have  small  hands,  are  established  opinions.  It  seems 
very  unlikely  that  in  the  absence  of  any  such  connexion, 
the  size  of  the  hand  should  have  come  to  be  generally  re- 
garded as  some  index  of  extraction.  That  there  exists  a  like 
relation  between  habitual  use  of  the  feet  and  largeness  of  the 


HEREDITY.  311 

feet,  we  have  strong  evidence  in  the  customs  of  the  Chinese. 
The  torturing  practice  of  artificially  arresting  the  growth  of 
the  feet,  could  never  have  become  established  among  the 
ladies  of  China,  had  they  not  seen  that  a  small  foot  was 
significant  of  superior  rank — that  is  of  a  luxurious  life — that 
is  of  a  life  without  bodily  labour.  There  is  evidence, 

too,  that  modifications  of  the  eyes,  caused  by  particular  uses 
of  the  eyes,  are  inherited.  Short  sight  appears  to  be  un- 
common among  peasants;  but  it  is  frequent  among  classes 
who  use  their  eyes  much  for  reading  and  writing,  and  is 
often  congenital.  Still  more  marked  is  this  relation  in 
Germany.  There,  the  educated  are  notoriously  studious,  and 
judging  from  the  numbers  of  young  Germans  who  wear 
spectacles,  there  is  reason  to  think  that  congenital  myopia  is 
very  frequent  among  them. 

Some  of  the  best  illustrations  of  functional  heredity,  are 
furnished  by  mental  characteristics.  Certain  powers  which 
mankind  have  gained  in  the  course  of  civilization  cannot,  I 
think,  be  accounted  for  without  admitting  the  inheritance  of 
acquired  modifications.  The  musical  faculty  is  one  of  these. 
To  say  that  "  natural  selection "  has  developed  it  by  pre- 
serving the  most  musically  endowed,  seems  an  inadequate 
explanation.  Even  now  that  the  development  and  pre- 
valence of  the  faculty  have  made  music  an  occupation  by 
which  the  most  musical  can  get  sustenance  and  bring  up 
families;  it  is  very  questionable  whether,  taking  the  musical 
career  as  a  whole,  it  has  any  advantage  over  other  careers  in 
the  struggle  for  existence  and  multiplication.  Still  more 
if  we  look  back  to  those  early  stages  through  which  the 
faculty  must  have  passed  before  definite  perception  of  melody 
was  arrived  at,  we  fail  to  see  how  those  possessing  the  rudi- 
mentary faculty  in  a  somewhat  greater  degree  than  the  rest, 
would  thereby  be  enabled  the  better  to  maintain  themselves 
and  their  children.  There  is  no  explanation  but  that  the 
habitual  association  of  certain  cadences  of  speech  with 
certain  emotions,  has  slowly  established  in  the  race  an 


312  THE  INDUCTIONS  OP  BIOLOGY. 

organized  and  inherited  connection  between  such  cadences 
and  such  emotions;  that  the  combination  of  such  cadences, 
more  or  less  idealized,  which  constitutes  melody,  has  all 
along  had  a  meaning  in  the  average  mind,  only  because  of  the 
meaning  which  cadences  had  acquired  in  the  average  mind; 
and  that  by  the  continual  hearing  and  practice  of  melody  there 
has  been  gained  and  transmitted  an  increasing  musical  sensi- 
bility. Confirmation  of  this  view  may  be  drawn 
from  individual  cases.  Grant  that  among  a  people  en- 
dowed with  musical  faculty  to  a  certain  degree,  spontaneous 
variation  will  occasionally  produce  men  possessing  it  in  a 
higher  degree;  it  cannot  be  granted  that  spontaneous  varia- 
tion accounts  for  the  frequent  production,  by  such  highly- 
endowed  men,  of  men  still  more  highly  endowed.  On  the 
average,  the  children  of  marriages  with  others  not  similarly 
endowed,  will  be  less  distinguished  rather  than  more  distin- 
guished. The  most  that  can  be  expected  is  that  this  unusual 
amount  of  faculty  shall  re-appear  in  the  next  generation  un- 
diminished.  How  then  shall  we  explain  cases  like  those  of 
Bach,  Mozart,  and  Beethoven,  all  of  them  sons  of  men  having 
unusual  musical  powers  who  were  constantly  exercising  those 
powers,  and  who  greatly  excelled  their  fathers  in  their  musical 
powers  ?  What  shall  we  say  to  the  facts  that  Haydn  was  the 
son  of  an  organist,  that  Hummel  was  born  to  a  music  master, 
and  that  Weber's  father  was  a  distinguished  violinist?  The 
occurrence  of  so  many  cases  in  one  nation  within  a  short 
period  of  time,  cannot  rationally  be  ascribed  to  the  coincidence 
of  "  spontaneous  variations."  It  can  be  ascribed  to  nothing 
but  inherited  developments  of  structure  caused  by  augmenta- 
tions of  function. 

But  the  clearest  proof  that  structural  alterations  caused  by 
alterations  of  function  are  inherited,  occurs  when  the  alter- 
ations are  morbid.  I  had  originally  named  in  this  place  the 
results  of  M.  Brown-Sequard's  experiments  on  guinea-pigs, 
showing  that  those  which  had  been  artificially  made  epileptic 
had  offspring  which  were  epileptic;  and  I  name  them  again 
though  his  inference  is  by  many  rejected.  For,  as  exemplified 


HEREDITY.  313 

a  few  pages  back,  strong  evidence  is  often  disregarded  for 
trivial  reasons  by  those  who  dislike  the  conclusion  drawn. 
Just  naming  this  evidence  and  its  possible  invalidity,  let  me 
pass  to  some  results  of  experiences  recently  set  forth  by  Dr. 
Savage,  President  of  the  Neurological  Society.  In  an  essay 
on  "  Heredity  and  Neurosis'"  published  in  Brain,  Parts 
LXXVII,  LXXVIII,  1897,  he  says:— "We  recognise  the 
transmission  of  a  tendency  to  develop  gout,  and  we  recognise 
that  the  disease  produced  by  the  individual  himself  differs 
little  from  that  which  may  have  been  inherited."  [That  is, 
acquired  'gout  may  be  transmitted  as  constitutional  gout.] 
"  I  have  seen  several  patients  whose  history  I  have  been  able 
to  examine  carefully,  in  whom  mental  tricks  have  been  trans- 
mitted from  one  generation  to  another."  In  the  "  musical 
prodigies  "  descending  from  musical  parents,  "  there  seemed 
to  be  a  transmission  of  a  greatly  increased  aptitude  or 
tendency  which  is  all  one  is  contending  for."  "  Though  there 
is,  in  my  opinion,  power  to  transmit  acquired  peculiarities, 
yet  the  tendency  is  to  transmit  a  predisposition."  (pp.19 — 
21.)  And  an  authority  on  nervous  diseases  who  is  second  to 
none — Dr.  Hughlings  Jackson — takes  the  same  view.  The 
liability  to  consumption  shown  by  children  of  consumptive 
parents,  which  no  one  doubts,  shows  us  the  same  thing.  It 
is  admitted  that  consumption  may  be  produced  by  condi- 
tions very  unfavourable  to  life ;  and  unless  it  is  held  that  the 
disease  so  produced  differs  from  the  disease  when  inherited, 
the  conclusion  must  be  that  here,  too,  there  is  a  transmission 
of  functionally-produced  organic  changes.  This  holds  true 
whether  the  production  of  tubercle  is  due  to  innate  defect  or 
whether  it  is  due  to  the  invasion  of  a  bacillus.  For  in  this  last 
case  the  consumptive  diathesis  must  be  regarded  as  a  state  of 
body  more  than  usually  liable  to  invasion  by  the  bacillus,  and 
this  is  the  same  when  acquired  as  when  transmitted. 

§  83.  Two  modified  manifestations  of  Heredity  remain  to 
be  noticed.  The  one  is  the  re-appearance  in  offspring  of  traits 
not  borne  by  the  parents,  but  borne  by  the  grandparents  or 


314  THE  INDUCTIONS  OP  BIOLOGY. 

by  remoter  ancestors.  The  other  is  the  limitation  of  Heredity 
by  sex — the  restriction  of  transmitted  peculiarities  to  off- 
spring of  the  same  sex  as  the  parent  possessing  them. 

Atavism,  which  is  the  name  given  to  the  recurrence  of 
ancestral  traits,  is  proved  by  many  and  varied  facts.  In  the 
picture-galleries  of  old  families,  and  on  the  monumental 
brasses  in  the  adjacent  churches,  are  often  seen  types  of  fea- 
ture which  are  still,  from  time  to  time,  repeated  in  members  of 
these  families.  It  is  a  matter  of  common  remark  that  some 
constitutional  diseases,  such  as  gout  and  insanity,  after  miss- 
ing a  generation,  will  show  themselves  in  the  next.  Dr. 
Struthers,  in  his  above-quoted  paper  "  On  Variation  in  the 
Number  of  Fingers  and  Toes,  and  in  the  Phalanges  in  Man," 
gives  cases  of  malformations  common  to  grandparent  and 
grandchild,  but  of  which  the  parent  had  no  trace.  M.  Girou 
(as  quoted  by  Mr.  Sedgwick)  says — "  One  is  often  surprised  to 
see  lambs  black,  or  spotted  with  black,  born  of  ewes  and  rams 
with  white  wool,  but  if  one  takes  the  trouble  to  go  back  to  the 
origin  of  this  phenomena,  it  is  found  in  the  ancestors." 
Instances  still  more  remarkable,  in  which  the  remoteness  of 
the  ancestors  copied  is  very  great,  are  given  by  Mr.  Darwin. 
He  points  out  that  in  crosses  between  varieties  of  the  pigeon, 
there  will  sometimes  re-appear  the  plumage  of  the  original 
rock-pigeon,  from  which  these  varieties  descended;  and  he 
thinks  the  faint  zebra-like  markings  occasionally  traceable  in 
horses  have  probably  a  like  meaning. 

The  other  modified  manifestation  of  heredity  above  referred 
to  is  the  limitation  of  heredity  by  sex.  In  Mr.  Sedgwick's 
essays,  already  named,  will  be  found  evidence  implying  that 
there  exists  some  such  tendency  to  limitation,  which  does  or 
does  not  show  itself  distinctly  according  to  the  nature  of  the 
organic  modification  to  be  conveyed.  On  joining  to  the  evi- 
dence he  gives  certain  bodies  of  allied  evidence  we  shall,  I 
think,  find  the  inconsistences  comprehensible. 

Beyond  the  familiar  facts  that  in  ourselves,  along  with  the 
essential  organs  of  sex  there  go  minor  structures  and  traits 


HEREDITY.  315 

distinctive  of  sex,  such  as  the  beard  and  the  voice  in  man, 
we  have  numerous  cases  in  which,  along  with  different  sex- 
organs  there  go  general  differences,  sometimes  immense  and 
often  conspicuous.  We  have  those  in  which  (as  in  sundry 
parasites)  the  male  is  extremely  small  compared  with  the 
female;  we  have  those  in  which  the  male  is  winged  and  the 
female  wingless;  we  have  those,  as  among  birds,  in  which 
the  plumage  of  males  contrasts  strongly  with  that  of  females ; 
and  among  butterflies  we  have  kindred  instances  in  which  the 
wings  of  the  two  sexes  are  wholly  unlike — some,  indeed,  in 
which  there  is  not  simply  dimorphism  but  polymorphism: 
two  kinds  of  females  both  differing  from  the  male.  How 
shall  we  range  these  facts  with  the  ordinary  facts  of  inheri- 
tance? Without  difficulty  if  heredity  results  from  the  pro- 
clivity which  the  component  units  contained  in  a  germ-cell  or 
a  sperm-cell  have  to  arrange  themselves  into  a  structure  like 
that  of  the  structure  from  which  they  were  derived.  For  the 
obvious  corollary  is  that  where  there  is  gamogenesis  there 
will  result  partly  concurring  and  partly  conflicting  proclivities. 
In  the  fertilized  germ  we  have  two  groups  of  physiological 
units,  slightly  different  in  their  structures.  These  slightly- 
different  units  severally  multiply  at  the  expense  of  the  nutri- 
ment supplied  to  the  unfolding  germ — each  kind  moulding 
this  nutriment  into  units  of  its  own  type.  Throughout  the 
process  of  development  the  two  kinds  of  units,  mainly  agree- 
ing in  their  proclivities  and  in  the  form  which  they  tend  to 
build  themselves  into,  but  having  minor  differences,  work 
in  unison  to  produce  an  organism  of  the  species  from  which 
they  were  derived,  but  work  in  antagonism  to  produce  copies 
of  their  respective  parent-organisms.  And  hence  ultimately 
results  an  organism  in  which  traits  of  the  one  are  mixed 
with  traits  of  the  other;  and  in  which,  according  to  the  pre- 
dominance of  one  or  other  group  of  units,  one  or  other  sex 
with  all  its  concomitants  is  produced. 

If  so,  it  becomes  comprehensible  that  with  the  predomi- 
nance of  either  group,  and  the  production  of  the  same  sex  as 


316  THE  INDUCTIONS  OF  BIOLOGY. 

that  of  the  parent  whence  it  was  derived,  there  will  go  the 
repetition  not  only  of  the  minor  sex-traits  of  that  parent  but 
also  of  any  peculiarities  he  o*  she  possessed,  such  as  monstros- 
ities. Since  the  two  groups  are  nearly  balanced,  and  since 
inheritance  is  never  an  average  of  the  two  parents  but  a 
mixture  of  traits  of  the  one  with  traits  of  the  other,  it  is  not 
difficult  to  see  why  there  should  be  some  irregularity  in  the 
transmission  of  these  monstrosities  and  constitutional  tend- 
encies, though  they  are  most  frequently  transmitted  only  to 
those  of  the  same  sex.* 

§  84.  Unawares  in  the  last  paragraph  there  has  been  taken 
for  granted  the  truth  of  that  suggestion  concerning  Heredity 
ventured  in  §  66.  Anything  like  a  positive  explanation  is 
not  to  be  expected  in  the  present  stage  of  Biology,  if  at  all. 
We  can  look  for  nothing  beyond  a  simplification  of  the 
problem;  and  a  reduction  of  it  to  the  same  category  with 
certain  other  problems  which  also  admit  of  hypothetical  solu- 
tions only.  If  an  hypothesis  which  sundry  widespread  phe- 
nomena have  already  thrust  upon  us,  can  be  shown  to  render 
the  phenomena  of  Heredity  more  intelligible  than  they  at 
present  seem,  we  shall  have  reason  to  entertain  it.  The  ap- 
plicability of  any  method  of  interpretation  to  two  different  but 
allied  classes  of  facts,  is  evidence  of  its  truth. 

The  power  which  many  animals  display  of  reproducing 
lost  parts,  we  saw  to  be  inexplicable  except  on  the  assump- 
tion that  the  units  of  which  any  organism  is  built  have  a 
tendency  to  arrange  themselves  into  the  shape  of  that  organ- 
ism (§65).  This  power  is  sufficiently  remarkable  in  cases 

*  In  addition  to  the  numerous  illustrations  given  by  Mr.  Scdgwick,  here 
is  one  which  Colonel  A.  T.  Eraser  published  in  Nature  for  Nov.  9,  1893, 
concerning  two  Hindoo  dwarfs : — "  In  speech  and  intelligence  the  dwarfs  were 
indistinguishable  from  ordinary  natives  of  India.  From  an  interrogation  of 
one  of  them,  it  appeared  that  he  belonged  to  a  family  all  the  male  members 
of  which  have  been  dwarfs  for  several  generations.  They  marry  ordinary 
native  girls,  and  the  female  children  grow  up  like  those  of  other  people.  The 
males,  however,  though  they  develop  at  the  normal  rate  until  they  reach  the 
age  of  six,  then  cease  to  grow,  and  become  dwarfs." 


HEREDITY.  317 

where  a  lost  limb  or  tail  is  replaced,  but  it  is  still  more 
remarkable  in  cases  where,  as  among  some  annelids,  the 
pieces  into  which  an  individual  is  cut  severally  complete 
themselves  by  developing  heads  and  tails,  or  in  cases  like 
that  of  the  Holothuria,  which  having,  when  alarmed,  ejected 
its  viscera,  reproduces  them.  Such  facts  compel  us  to  admit 
that  the  components  of  an  organism  have  a  proclivity 
towards  a  special  structure — that  the  adult  organism  when 
mutilated  exhibits  that  same  proclivity  which  is  exhibited 
by  the  young  organism  in  the  course  of  its  normal  develop- 
ment. As  before  said,  we  may,  for  want  of  a  better  name, 
figuratively  call  this  power  organic  polarity:  meaning  by 
this  phrase  nothing  more  than  the  observed  tendency  towards 
a  special  arrangement.  And  such  facts  as  those  presented 
by  the  fragments  of  a  Hydra,  and  by  fragments  of  leaves 
from  which  complete  plants  are  produced,  oblige  us  to  recog- 
nize this  proclivity  as  existing  throughout  the  tissues  in 
general — nay,  in  the  case  of  the  Begonia  phyllomaniaca, 
obliges  us  to  recognize  this  proclivity  as  existing  in  the 
physiological  units  contained  in  each  undifferentiated 
cell.  Quite  in  harmony  with  this  conclusion,  are 

certain  implications  since  noticed,  respecting  the  characters 
of  sperm-cells  and  germ-cells.  We  saw  sundry  reasons  for 
rejecting  the  supposition  that  these  are  highly-specialized 
cells  and  for  accepting  the  opposite  supposition,  that  they 
are  cells  differing  from  others  rather  in  being  unspecialized. 
And  here  the  assumption  to  which  we  seem  driven  by  the 
ensemble  of  the  evidence,  is,  that  sperm-cells  and  germ-cells 
are  essentially  nothing  more  than  vehicles  in  which  are  con- 
tained small  groups  of  the  physiological  units  in  a  fit  state 
for  obeying  their  proclivity  towards  the  structural  arrange- 
ment of  the  species  they  belong  to. 

If  the  likeness  of  offspring  to  parents  is  thus  determined, 
it  becomes  manifest,  a  priori,  that  besides  the  transmission  of 
generic  and  specific  peculiarities,  there  will  be  a  transmis- 
sion of  those  individual  peculiarities  which,  arising  without 


318  THE   INDUCTIONS  OF   BIOLOGY. 

assignable  causes,  are  classed  as  "  spontaneous."  For  if  the 
assumption  of  a  special  arrangement  of  parts  by  an  organism, 
is  due  to  the  proclivity  of  its  physiological  units  towards  that 
arrangement;  then  the  assumption  of  an  arrangement  of 
parts  slightly  different  from  that  of  the  species,  implies 
physiological  units  slightly  unlike  those  of  the  species;  and 
these  slightly-unlike  physiological  units,  communicated 
through  the  medium  of  sperm-cell  or  germ-cell,  will  tend,  in 
the  offspring,  to  build  themselves  into  a  structure  similarly 
diverging  from  the  average  of  the  species. 

But  it  is  not  equally  manifest  that,  on  this  hypothesis, 
alterations  of  structure  caused  by  alterations  of  function 
must  be  transmitted  to  offspring.  It  is  not  obvious  that 
change  in  the  form  of  a  part,  caused  by  changed  action,  in- 
volves such  change  in  the  physiological  units  throughout  the 
organism  that  these,  when  groups  of  them  are  thrown  off  in 
the  shape  of  reproductive  centres,  will  unfold  into  organisms 
that  have  this  part  similarly  changed  in  form.  Indeed,  when 
treating  of  Adaptation  (§  69),  we  saw  that  an  organ  modified 
by  increase  or  decrease  of  function,  can  but  slowly  re-act  on 
the  system  at  large,  so  as  to  bring  about  those  correlative 
changes  required  to  produce  a  new  equilibrium;  and  yet  only 
when  such  new  equilibrium  has  been  established,  can  we  ex- 
pect it  to  be  fully  expressed  in  the  modified  physiological  units 
of  which  the  organism  is  built — only  then  can  we  count 
on  a  complete  transfer  of  the  modification  to  descendants. 
Nevertheless,  that  changes  of  structure  caused  by  changes 
of  action  must  also  be  transmitted,  however  obscurely,  ap- 
pears to  be  a  deduction  from  first  principles — or  if  not  a 
specific  deduction,  still,  a  general  implication.  For  if  an 
organism  A,  has,  by  any  peculiar  habit  or  condition  of  life, 
been  modified  into  the  form  A',  it  follows  that  all  the  func- 
tions of  A',  reproductive  function  included,  must  be  in  some 
degree  different  from  the  functions  of  A.  An  organism 
being  a  combination  of  rhythmically-acting  parts  in  moving 
equilibrium,  the  action  and  structure  of  any  one  part  cannot 


HEREDITY.  319 

be  altered  without  causing  alterations  of  action  and  struc- 
ture in  all  the  rest;  just  as  no  member  of  the  Solar  System 
could  be  modified  in  motion  or  mass,  without  producing  re- 
arrangements throughout  the  whole  Solar  System.  And  if 
the  organism  A,  when  changed  to  A',  must  be  changed  in  all 
its  functions ;  then  the  offspring  of  A'  cannot  be  the  same 
as  they  would  have  been  had  it  retained  the  form  A.  That 
the  change  in  the  offspring  must,  other  things  equal,  be  in 
the  same  direction  as  the  change  in  the  parent,  appears 
implied  by  the  fact  that  the  change  propagated  throughout 
the  parental  system  is  a  change  towards  a  new  state  of 
equilibrium — a  change  tending  to  bring  the  actions  of  all 
organs,  reproductive  included,  into  harmony  with  these  new 
actions.  Or,  bringing  the  question  to  its  ultimate  and  sim- 
plest form,  we  may  say  that  as,  on  the  one  hand,  physiological 
units  will,  because  of  their  special  polarities,  build  them- 
selves into  an  organism  of  a  special  structure;  so,  on  the 
other  hand,  if  the  structure  of  this  organism  is  modified 
by  modified  function,  it  will  impress  some  corresponding 
modification  on  the  structures  and  polarities  of  its  units.  The 
units  and  the  aggregate  must  act  and  re-act  on  each  other. 
If  nothing  prevents,  the  units  will  mould  the  aggregate  into 
a  form  in  equilibrium  with  their  pre-existing  polarities.  If, 
contrariwise,  the  aggregate  is  made  by  incident  actions  to 
take  a  new  form,  its  forces  must  tend  to  re-mould  the  units 
into  harmony  with  this  new  form.  And  to  say  that  the 
physiological  units  are  in  any  degree  so  re-moulded  as  to 
bring  their  polar  forces  towards  equilibrium  with  the  forces  of 
the  modified  aggregate,  is  to  say  that  when  separated  in  the 
shape  of  reproductive  centres,  these  units  will  tend  to  build 
themselves  up  into  an  aggregate  modified  in  the  same  direc- 
tion. 

NOTE. — A  large  amount  of  additional  evidence  supporting 
the  belief  that  functionally  produced  modifications  are  in- 
herited, will  be  found  in  Appendix  B. 


CHAPTER  JX. 

VARIATION. 

§  85.  EQUALLY  conspicuous  with  the  truth  that  every 
organism  bears  a  general  likeness  to  its  parents,  is  the  truth 
that  no  organism  is  exactly  like  either  parent.  Though 
similar  to  both  in  generic  and  specific  traits,  and  usually,  too, 
in  those  traits  which  distinguish  the  variety,  it  diverges  in 
numerous  traits  of  minor  importance.  No  two  plants  are 
indistinguishable;  and  no  two  animals  are  without  differ- 
ences. Variation  is  co-extensive  with  Heredity. 

The  degrees  of  variation  have  a  wide  range.  There  are 
deviations  so  small  as  to  be  not  easily  detected;  and  there 
are  deviations  great  enough  to  be  called  monstrosities.  In 
plants  we  may  pass  from  cases  of  slight  alteration  in  the 
shape  of  a  leaf,  to  cases  where,  instead  of  a  flower  with  its 
calyx  above  the  seed-vessel,  there  is  produced  a  flower  with 
its  calyx  below  the  seed-vessel ;  and  while  in  one  animal  \ 
there  arises  a  scarcely  noticeable  unlikeness  in  the  length  or 
colour  of  the  hair,  in  another  an  organ  is  absent  or  a 
supernumerary  organ  appears.  Though  small  variations 
are  by  far  the  most  general,  yet  variations  of  considerable 
magnitude  are  not  uncommon;  and  even  those  variations 
constituted  by  additions  or  suppressions  of  parts,  are  not  so 
rare  as  to  be  excluded  from  the  list  of  causes  by  which 
organic  forms  are  changed.  Cattle  without  horns  are  fre- 
quent. Of  sheep  there  are  horned  breeds  and  breeds  that 


VARIATION.  321 

have  lost  their  horns.  At  one  time  there  existed  in  Scot- 
land a  race  of  pigs  with  solid  feet  instead  of  cleft  feet.  In 
pigeons,  according  to  Mr.  Darwin,  "  the  number  of  the  caudal 
and  sacral  vertebra  vary;  as  does  the  number  of  the  ribs, 
together  with  their  relative  breadth  and  the  presence  of  pro- 
cesses." 

That  variations,  both  small  and  large,  which  arise  without 
any  specific  assignable  cause,  tend  to  become  hereditary,  was 
shown  in  the  last  chapter.  Indeed  the  evidence  which  proves 
Heredity  in  its  smaller  manifestations  is  the  same  evidence 
which  proves  Variation ;  since  it  is  only  when  there  occur  vari- 
ations that  the  inheritance  of  anything  beyond  the  structural 
peculiarities  of  the  species  can  be  proved.  It  remains  here, 
however,  to  be  observed  that  the  transmission  of  variations 
is  itself  variable;  and  that  it  varies  both  in  the  direction  of 
decrease  and  in  the  direction  of  increase.  An  individual  trait 
of  one  parent  may  be  so  counteracted  by  the  influence  of  the 
other  parent,  that  it  may  not  appear  in  the  offspring ;  or,  not 
being  so  counteracted,  the  offspring  may  possess  it,  perhaps 
in  an  equal  degree  or  perhaps  in  a  less  degree;  or  the  off- 
spring may  exhibit  the  trait  in  even  a  still  higher  degree. 
Among  illustrations  of  this,  one  must  suffice.  I  quote  it  from 
the  essay  by  Sir  J.  Struthers  referred  to  in  the  last  chapter. 

"  The  great-great-grandmother,  Esther  P (who  mar- 
ried A L ),  had  a  sixth  little  finger  on  one  hand.  Of 

their  eighteen  children  (twelve  daughters  and  six  sons),  only 
one  (Charles)  is  known  to  have  had  digital  variety.  We 
have  the  history  of  the  descendants  of  three  of  the  sons, 
Andrew,  Charles,  and  James. 

"  (1.)  Andrew  L had  two  sons,  Thomas  and  Andrew; 

and  Thomas  had  two  sons  all  without  digital  variety.  Here 
we  have  three  successive  generations  without  the  variety 
possessed  by  the  great-grandmother  showing  itself. 

"  (2.)  James  L ,  who  was  normal,  had  two  sons  and 

seven  daughters,  also  normal.  One  of  the  daughters  became 
Mrs.  J (one  of  the  informants),  and  had  three  daughters 


322  THE  INDUCTIONS  OF  BIOLOGY. 

and  five  sons,  all  normal  except  one  of  the  sons,  James  J , 

now  get.  17,  who  had  six  fingers  on  each  hand.    .    .    . 

"  In  this  branch  of  the  descendants  of  Esther,  we  see  it 
passing  over  two  generations  and  reappearing  in  one  member 
of  the  third  generation,  and  now  on  both  hands. 

"  (3.)   Charles  L ,  the  only  child  of  Esther  who  had 

digital  variety,  had  six  fingers  on  each  hand.  He  had  three 
sons,  James,  Thomas,  and  John,  all  of  whom  were  born  with 
six  fingers  on  each  hand,  while  John  has  also  a  sixth  toe  on 
one  foot.  He  had  also  five  other  sons  and  four  daughters,  all 
of  whom  were  normal. 

"  (a.)  Of  the  normal  children  of  this,  the  third  generation, 
the  five  sons  had  twelve  sons  and  twelve  daughters,  and  the 
four  daughters  have  had  four  sons  and  four  daughters,  being 
the  fourth  generation,  all  of  whom  were  normal.  A  fifth 
generation  in  this  sub-group  consists  as  yet  of  only  two  boys 
and  two  girls  who  are  also  normal. 

"  In  this  sub-branch,  we  see  the  variety  of  the  first  gener- 
ation present  in  the  second,  passing  over  the  third  and  fourth, 
and  also  the  fifth  as  far  as  it  has  yet  gone. 

"  (6.)  James  had  three  sons  and  two  daughters,  who  are 
normal. 

"  (c.)  Thomas  had  four  sons  and  five  daughters,  who  are 
normal;  and  has  two  grandsons,  also  normal. 
•  "  In  this  sub-branch  of  the  descent,  we  see  the  variety  of 
the  first  generation,  showing  itself  in  the  second  and  third, 
and  passing  over  the  fourth,  and  (as  far  as  it  yet  exists)  the 
fifth  generation. 

"  (d.)  John  L (one  of  the  informants)  had  six  fingers, 

the  additional  finger  being  attached  on  the  outer  side,  as  in 
the  case  of  his  brothers  James  and  Thomas.  All  of  them 
had  the  additional  digits  removed.  John  has  also  a  sixth  toe 
on  one  foot,  situated  on  the  outer  side.  The  fifth  and  sixth 
toes  have  a  common  proximal  phalange,  and  a  common  integu- 
ment invests  the  middle  and  distal  phalanges,  each  having  a 
separate  nail. 


VARIATION.  323 

"  John  L has  a  son  who  is  normal,  and  a  daughter, 

Jane,  who  was  born  with  six  fingers  on  each  hand  and  six  toes 
on  each  foot.  The  sixth  fingers  were  removed.  The  sixth 
toes  are  not  wrapped  with  the  fifth  as  in  her  father's  case, 
but  are  distinct  from  them.  The  son  has  a  son  and  daughter, 
who,  like  himself,  are  normal. 

"  In  this,  the  most  interesting  sub-branch  of  the  descent, 
we  see  digital  increase,  which  appeared  in  the  first  generation 
on  one  limb,  appearing  in  the  second  on  two  limbs,  the  hands ; 
in  the  third  on  three  limbs,  the  hands  and  one  foot;  in 
the  fourth  on  all  the  four  limbs.  There  is  as  yet  no  fifth 
generation  in  uninterrupted  transmission  of  the  variety.  The 
variety  does  not  yet  occur  in  any  member  of  the  fifth  genera- 
tion of  Esther's  descendants,  which  consists,  as  yet,  only  of 
three  boys  and  one  girl,  whose  parents  were  normal,  and  of 
two  boys  and  two  girls,  whose  grandparents  were  normal.  It 
is  not  known  whether  in  the  case  of  the  great-great-grand- 
mother, Esther  P ,  the  variety  was  original  or  inherited."  * 

§  8G.  Where  there  is  great  uniformity  among  the  members 
of  a  species,  the  divergences  of  offspring  from  the  average 
type  are  usually  small;  but  where,  among  the  members  of  a 
species,  considerable  unlikenesses  have  once  been  established, 
unlikenesses  among  the  offspring  are  frequent  and  great. 
Wild  plants  growing  in  their  natural  habitats  are  uniform 
over  large  areas,  and  maintain  from  generation  to  generation 
like  structures;  but  when  cultivation  has  caused  appreciable 
differences  among  the  members  of  any  species  of  plant,  ex- 
tensive and  numerous  deviations  are  apt  to  arise.  Similarly, 
between  wild  and  domesticated  animals  of  the  same  species, 
we  see  the  contrast  that  though  the  homogeneous  wild  race 

*  This  remarkable  case  appears  to  militate  against  the  conclusion,  drawn 
a  few  pages  back,  that  the  increase  of  a  peculiarity  by  coincidence  of  "  spon- 
taneous variations  "  in  successive  generations,  is  very  improbable ;  and  that 
the  special  superiorities  of  musical  composers  cannot  have  thus  arisen.  The 
reply  is  that  the  extreme  frequency  of  the  occurrence  among  so  narrow  a  class 
as  that  of  musical  composers,  forbids  the  interpretation  thus  suggested. 


324  THE  INDUCTIONS  OP  BIOLOGY. 

maintains  its  type  with  great  persistence,  the  comparatively 
heterogeneous  domestic  race  frequently  produces  individuals 
more  unlike  the  average  type  than  the  parents  are. 

Though  unlikeness  among  progenitors  is  one  antecedent  of 
variation,  it  is  by  no  means  the  sole  antecedent.  Were  it 
so,  the  young  dnes  successively  born  to  the  same  parents  would 
be  alike.  If  any  peculiarity  in  a  new  organism  were  a  direct 
resultant  of  the  structural  differences  between  the  two  organ- 
isms which  produced  it;  then  all  subsequent  new  organisms 
produced  by  these  two  would  show  the  same  peculiarity.  But 
we  know  that  the  successive  offspring  have  different  peculiari- 
ties :  no  two  of  them  are  ever  exactly  alike. 

One  cause  of  such  structural  variation  in  progeny,  is  func- 
tional variation  in  parents.  Proof  of  this  is  given  by  the  fact 
that,  among  progeny  of  the  same  parents,  there  is  more  differ- 
ence between  those  begotten  under  different  constitutional 
states  than  between  those  begotten  under  the  same  constitu- 
tional state.  It  is  notorious  that  twins  are  more  nearly  alike 
than  children  borne  in  succession.  The  functional  conditions 
of  the  parents  being  the  same  for  twins,  but  not  the  same  for 
their  brothers  and  sisters  (all  other  antecedents  being  constant), 
we  have  no  choice  but  to  admit  that  variations  in  the  func- 
tional conditions  of  the  parents,  are  the  antecedents  of  those 
greater  unlikenesses  which  their  brothers  and  sisters  exhibit. 

Some  other  antecedent  remains,  however.  The  parents 
being  the  same,  and  their  constitutional  states  the  same,  vari- 
ation, more  or  less  marked,  still  manifests  itself.  Plants 
grown  from  seeds  out  of  one  pod,  or  animals  produced  at  one 
birth,  are  not  alike.  Sometimes  they  differ  considerably. 
In  a. litter  of  pigs  or  of  kittens,  we  rarely  see  uniformity  of 
markings;  and  occasionally  there  are  important  structural 
contrasts.  I  have  myself  recently  been  shown  a  litter  of  New- 
foundland puppies,  some  of  which  had  four  digits  to  their 
feet,  while  in  others  there  was  present,  on  each  hind-foot, 
what  is  called  the  "  dew-claw  " — a  rudimentary  fifth  digit. 

Thus,  induction  points  to  three  causes  of  variation,  all  in 


VARIATION.  325 

action  together.  We  have  heterogeneity  among  progenitors, 
which,  did  it  act  uniformly  and  alone  in  generating,  by  com- 
position of  forces,  new  deviations,  would  impress  such  new 
deviations  to  the  same  extent  on  all  offspring  of  the  same 
parents;  which  it  does  not.  We  have  functional  variation 
in  the  parents,  which,  acting  either  alone  or  in  combination 
with  the  preceding  cause,  would  entail  the  same  structural 
variations  on  all  young  ones  simultaneously  produced ;  which 
it  does  not.  Consequently  there  is  some  third  cause  of  varia- 
tion, yet  to  be  found,  which  acts  along  with  the  structural 
and  functional  variations  of  ancestors  and  parents. 

§  87.  Already,  in  the  last  section,  there  has  been  implied 
some  relation  between  variation  and  the  action  of  external 
conditions.  The  above-cited  contrast  between  the  uniformity 
of  a  wild  species  and  the  multiformity  of  the  same  species 
when  cultivated  or  domesticated,  thrusts  this  truth  upon  us. 
Eespecting  the  variations  of  plants,  Mr.  Darwin  remarks  that 
"  '  sports  '  are  extremely  rare  under  nature,  but  far  from  rare 
under  cultivation."  Others  who  have  studied  the  matter 
assert  that  if  a  species  of  plant  which,  up  to  a  certain  time, 
has  maintained  great  uniformity,  once  has  its  constitution 
thoroughly  disturbed,  it  will  go  on  varying  indefinitely. 
Though,  in  consequence  of  the  remoteness  of  the  periods  at 
which  they  were  domesticated,  there  is  a  lack  of  positive 
proof  that  our  extremely  variable  domestic  animals  have  be- 
come variable  under  the  changed  conditions  implied  by  domes- 
tication, having  been  previously  constant;  yet  competent 
judges  do  not  doubt  that  this  has  been  the  case. 

Now  the  constitutional  disturbance  which  precedes  varia- 
tion, can  be  nothing  else  than  an  overthrowing  of  the  pre- 
established  equilibrium  of  functions.  Transferring  a  plant 
from  forest  lands  to  a  ploughed  field  or  a  manured  garden,  is 
altering  the  balance  of  forces  to  which  it  has  been  hitherto 
subject,  by  supplying  it  with  different  proportions  of  the 
assimilable  matters  it  requires,  and  taking  away  some  of  the 
22 


326  THE  INDUCTIONS  OF  BIOLOGY. 

positive  impediments  io  its  growth  which  competing  wild 
plants  before  offered_.  An  animal  taken  from  woods  or  plains, 
where  it  lived  on  wild  food  of  its  own  procuring,  and  placed 
under  restraint  while  artificially  supplied  with  food  not  quite 
like  what  it  had  before,  is  an  animal  subject  to  new  outer 
actions  to  which  its  inner  actions  must  be  adjusted.  From 
the  general  law  of  equilibration  we  found  it  to  follow  that 
"the  maintenance  of 'such  a  moving  equilibrium"  as  an 
organism  displays,  "  requires  the  habitual  genesis  of  internal 
forces  corresponding  in  number,  directions,  and  amounts,  to 
the  external  incident  forces — as  many  inner  functions,  single 
or  combined,  as  there  are  single  or  combined  outer  actions  to 
be  met  "  (First  Principles,  §  173) ;  and  more  recently  (§27), 
we  have  seen  that  Life  itself  is  "  the  definite  combination  of 
heterogeneous  changes,  both  simultaneous  and  successive,  in 
correspondence  with  external  co-existences  and  sequences." 
Necessarily,  therefore,  an  organism  exposed  to  a  permanent 
change  in  the  arrangement  of  outer  forces  must  undergo  a 
permanent  change  in  the  arrangement  of  inner  forces.  The 
old  equilibrium  has  been  destroyed;  and  a  new  equilibrium 
must  be  established.  There  must  be  functional  perturbations, 
ending  in  a  re-adjusted  balance  of  functions. 

If,  then,  change  of  conditions  is  the  only  known  cause  by 
which  the  original  homogeneity  of  a  species  is  destroyed; 
and  if  change  of  conditions  can  affect  an  organism  only  by 
altering  its  functions;  it  follows  that  alteration  of  func- 
tions is  the  only  known  internal  cause  to  which  the  com- 
mencement of  variation  can  be  ascribed.  That  such  minor 
functional  changes  as  parents  undergo  from  year  to  year  are 
influential  on  the  offspring,  we  have  seen  is  proved  by  the 
greater  unlikeness  that  exists  between  children  born  to  the 
same  parents  at  different  times,  than  exists  between  twins. 
And  here  we  seem  forced  to  conclude  that  the  larger  func- 
tional variations  produced  by  greater  external  changes,  are 
the  initiators  of  those  structural  variations  which,  when 
once  commenced  in  a  species,  lead  by  their  combinations  and 


VARIATION.  327 

antagonisms  to  multiform  results.  Whether  they  are  or 
are  not  the  direct  initiators,  they  must  still  be  the  indirect 
initiators. 

§  87 a.  In  the  foregoing  sentence  those  pronounced  struc- 
tural variations  from  which  may  presently  arise  new  varieties 
and  eventually  species,  are  ascribed  to  "  the  larger  functional 
variations  produced  by  greater  external  changes  "  ;  and  this 
limitation  is  a  needful  one,  since  there  is  a  constant  cause  of 
minor  variations  of  a  wholly  different  kind. 

There  are  the  variations  arising  from  differences  in  the 
conditions  to  which  the  germ  is  subject,  both  before  detach- 
ment from  the  parent  and  after.  At  first  sight  it  seems  that 
plants  grown  from  seeds  out  of  the  same  seed-vessel  and  ani- 
mals belonging  to  the  same  litter,  ought,  in  the  absence  of  . 
any  differences  of  ancestral  antecedents,  to  be  entirely  alike. 
But  this  is  not  so.  Inevitably  they  are  subject  from  the  very 
outset  to  slightly  different  sets  of  agencies.  The  seeds  in  a 
seed-vessel  do  not  stand  in  exactly  the  same  relations  to  the 
sources  of  nutriment:  some  are  nearer  than  others.  They 
are  somewhat  differently  exposed  to  the  heat  and  light  pene- 
trating their  envelope;  and  some  are  more  impeded  in  their 
growth  by  neighbours  than  others  are.  Similarly  with 
young  animals  belonging  to  the  same  litter.  Their  uterine 
lives  are  made  to  some  extent  unlike  by  unlike  connexions 
with  the  blood-supply,  by  mutual  interferences  not  all  the 
same,  and  even  by  different  relations  to  the  disturbances 
caused  by  the  mother's  movements.  So,  too,  is  it  after 

separation  from  the  parent  plant  or  animal.  Even  the 
biblical  parable  reminds  us  that  seeds  fall  into  places  here 
favourable  and  there  unfavourable  in  various  degrees.  In 
respect  of  soil,  in  respect  of  space  for  growth,  in  respect 
of  shares  of  light,  none  of  them  are  circumstanced  in  quite 
the  same  ways.  With  animals  the  like  holds.  In  a  litter  of 
pigs  some,  weaker  than  others,  do  not  succeed  as  often  in 
getting  possession  of  teats.  And  then  in  both  cases  the 


328  THE  INDUCTIONS  OF  BIOLOGY. 

differences  thus  initiated  become  increasingly  pronounced. 
Among  young  plants  the  smaller,  outgrown  by  their  better- 
placed  neighbours,  are  continually  more  shaded  and  more  left 
behind;  and  among  the  litter  the  weakly  ones,  continually 
thrust  aside  by  the  stronger,  become  relatively  more  weakly 
from  deficient  nutrition. 

Differentiations  thus  arising,  both  before  and  after  separa- 
tion from  parents,  though  primarily  differences  of  growth, 
entail  structural  differences ;  for  it  is  a  general  law  of  nutri- 
tion that  when  there  is  deficiency  of  food  the  non-essential 
organs  suffer  more  than  the  essential  ones,  and  the  unlike- 
nesses  of  proportion  hence  arising  constitute  unlikenesses  of 
structure.  It  may  be  concluded,  however,  that  variations 
generated  in  this  manner  usually  have  no  permanent  results. 
In  the  first  place,  the  individuals  which,  primarily  in  growth 
and  secondarily  in  smaller  developments  of  less-important 
organs,  are  by  implication  inferior,  are  likely  to  be  eliminated 
from  the  species.  In  the  second  place,  differences  of  struc- 
ture produced  in  the  way  shown  do  not  express  differences  of 
constitution — are  not  the  effects  of  somewhat  divergent 
physiological  units;  and  consequently  are  not  likely  to  be 
repeated  in  posterity. 

§  88.  We  have  still,  therefore,  to  explain  those  variations 
which  have  no  manifest  causes  of  the  kinds  thus  far  con- 
sidered. These  are  the  variations  termed  "  spontaneous." 
Not  that  those  who  apply  to  them  this  word,  or  some  equi- 
valent, mean  to  imply  that  they  are  uncaused.  Mr.  Darwin 
expressly  guards  himself  against  such  an  interpretation.  He 
says: — "I  have  hitherto  sometimes  spoken  as  if  the  varia- 
tions— so  common  and  multiform  in  organic  beings  under 
domestication,  and  in  a  lesser  degree  in  those  in  a  state  of 
nature — had  been  due  to  chance.  This,  of  course,  is  a  wholly 
incorrect  expression,  but  it  serves  to  acknowledge  plainly  our 
ignorance  of  the  cause  of  each  particular  variation."  Not 
only,  however,  do  I  hold,  in  common  with  Mr.  Darwin,  that 


VARIATION.  329 

there  must  be  some  cause  for  these  apparently-spontaneous 
variations,  but  it  seems  to  me  that  a  definite  cause  is  assign- 
able. I  think  it  may  be  shown  that  unlikenesses  must  neces- 
sarily arise  even  between  the  new  individuals  simultaneously 
produced  by  the  same  parents.  Instead  of  the  occurrence 
of  such  variations  being  inexplicable,  the  absence  of  them 
would  be  inexplicable. 

In  any  series  of  dependent  changes  a  small  initial  differ- 
ence often  works  a  marked  difference  in  the  results.  The  mode 
in  which  a  particular  breaker  bursts  on  the  beach,  may  deter- 
mine whether  the  seed  of  some  foreign  plant  which  it  bears 
is  or  is  not  stranded — may  cause  the  presence  or  absence  of 
this  plant  from  the  Flora  of  the  land ;  and  may  so  affect,  for 
millions  of  years,  in  countless  ways,  the  living  creatures 
throughout  the  land.  A  single  touch,  by  introducing  into 
the  body  some  morbid  matter,  may  set  up  an  immensely- 
involved  set  of  functional  disturbances  and  structural  alter- 
ations. The  whole  tenor  of  a  life  may  be  changed  by  a  word 
of  advice;  or  a  glance  may  determine  an  action  which  alters 
thoughts,  feelings,  and  deeds  throughout  a  long  series  of 
years.  In  those  still  more  involved  combinations  of  changes 
which  societies  exhibit,  this  truth  is  still  more  conspicuous. 
A  hair's-breadth  difference  in  the  direction  of  some  soldier's 
musket  at  the  battle  of  Arcola,  by  killing  Napoleon,  might 
have  changed  events  throughout  Europe ;  and  though  the  type 
of  social  organization  in  each  European  country  would  have 
been  now  very  much  what  it  is,  yet  in  countless  details  it 
would  have  been  different. 

Illustrations  like  these,  with  which  pages  might  be  filled, 
prepare  us  for  the  conclusion  that  organisms  produced  by 
the  same  parents  at  the  same  time,  must  be  more  or  less 
differentiated,  both  by  insensible  initial  differences  and  by 
slight  differences  in  the  conditions  to  which  they  are  subject 
during  their  evolution.  We  need  not,  however,  rest  with 
assuming  such  initial  differences :  the  necessity  of  them  is 
demonstrable.  The  individual  germ-cells  which,  in  succes- 


330  THE  INDUCTIONS  OP  BIOLOGY. 

i 

sion  or  simultaneously,  are  separated  from  the  same  parent, 
can  never  be  exactly  alike;  nor  can  the  sperm-cells  which 
fertilize  them.  When  treating  of  the  instability  of  the 
homogeneous  (First  Principles,  §  149),  we  saw  that  no  two 
parts  of  any  aggregate  can  be  similarly  conditioned  with  re- 
spect to  incident  forces;  and  that  being  subject  to  forces 
that  are  more  or  less  unlike,  they  must  become  more  or  less 
unlike.  Hence,  no  two  ova  in  an  ovarium  or  ovules  in  a 
seed-vessel — no  two  spermatozoa  or  pollen-cells,  can  be 
identical.  Whether  or  not  there  arise  other  contrasts,  there 
are  certain  to  arise  quantitative  contrasts;  since  the  process 
of  nutrition  cannot  be  absolutely  alike  for  all.  The  repro- 
ductive centres  must  begin  to  differentiate  from  the  very 
outset.  Such  being  the  necessities  of  the  case,  what 

will  happen  on  any  successive  or  simultaneous  fertilizations? 
Inevitably  unlikenesses  between  the  respective  parental  in- 
fluences must  result.  Quantitative  differences  among  the 
sperm-cells  and  among  the  germ-cells,  will  insure  this. 
Grant  that  the  number  of  physiological  units  contained  in 
any  one  reproductive  cell,  can  rarely  if  ever  be  exactly  equal 
to  the  number  contained  in  any  other,  ripened  at  the  same 
time  or  at  a  different  time;  and  it  follows  that  among  the 
fertilized  germs  produced  by  the  same  parents,  the  physiolo- 
gical units  derived  from  them  respectively  will  bear  a  dif- 
ferent numerical  ratio  to  each  other  in  every  case.  If  the 
parents  are  constitutionally  quite  alike,  the  variation  in  the 
ratio  between  the  units  they  severally  bequeath,  cannot  cause 
unlikenesses  among  the  offspring.  But  if  otherwise,  no  two 
of  the  offspring  can  be  alike.  In  every  case  the  small  initial 
difference  in  the  proportions  of  the  slightly-unlike  units,  will 
lead,  during  evolution,  to  a  continual  multiplication  of  differ- 
ences. The  insensible  divergence  at  the  outset  will  gene- 
rate sensible  divergences  at  the  conclusion.  Possibly 
some  may  hence  infer  that  though,  in  such  case,  the  off- 
spring must  differ  somewhat  from  each  other  and  from  both 
parents,  yet  that  in  every  one  of  them  there  must  result  a 


VARIATION.  331 

homogeneous  mixture  of  the  traits  of  the  two  parents.  A 
little  consideration  shows  that  the  reverse  is  inferable.  If, 
throughout  the  process  of  development,  the  physiological 
units  derived  from  each  parent  preserved  the  same  ratio  in 
all  parts  of  the  growing  organism,  each  organ  would  show  as 
much  as  every  other,  the  influence  of  either  parent.  But  no 
such  uniform  distribution  is  possible.  It  has  been  shown 
(First  Principles,  §163),  that  in  any  aggregate  of  mixed 
units  segregation  must  inevitably  go  on.  Incident  forces 
will  tend  ever  to  cause  separation  of  the  two  orders  of  units 
from  each  other — will  tend  to  integrate  groups  of  the  one 
order  in  one  place  and  groups  of  the  other  order  in  another 
place.  Hence  there  must  arise  not  a  homogeneous  mean 
between  the  two  parents,  but  a  mixture  of  organs,  some  of 
which  mainly  follow  the  one  and  some  the  other.  And  this 
is  the  kind  of  mixture  which  observation  shows  us. 

Still  it  may  be  fairly  objected  that  however  the  attributes 
of  the  two  parents  are  variously  mingled  in  their  offspring, 
they  must  in  all  of  them  fall  between  the  extremes  displayed 
in  the  parents.  In  no  characteristic  could  one  of  the  young 
exceed  both  parents,  were  there  no  cause  of  "  spontaneous 
variation  "  but  the  one  alleged.  Evidently,  then,  there  is  a 
cause  yet  unfound. 

§  89.  Thus  far  we  have  contemplated  the  process  under  its 
simplest  aspect.  While  we  have  assumed  the  two  parents  to 
be  somewhat  unlike,  we  have  assumed  that  each  parent  has  a 
homogeneous  constitution — is  built  up  of  physiological  units 
which  are  exactly  alike.  But  in  no  case  can  such  a  homo- 
geneity exist.  Each  parent  had  parents  who  were  more  or 
less  contrasted — each  parent  inherited  at  least  two  orders  of 
physiological  units  not  quite  identical.  Here  then  we  have 
a  further  cause  of  variation.  The  sperm-cells  or  germ-cells 
which  any  organism  produces,  will  differ  from  each  other  not 
quantitatively  only  but  qualitatively.  Of  the  slightly-unlike 
physiological  units  bequeathed  to  it,  the  reproductive  cells  it 


332  THE  INDUCTIONS  OF  BIOLOGY. 

casts  off  cannot  habitually  contain  the  same  proportions ;  and 
we  may  expect  the  proportions  to  vary  not  slightly  but 
greatly.  Just  as,  during  the  evolution  of  an  organism,  the 
physiological  units  derived  from  the  two  parents  tend  to 
segregate,  and  produce  likeness  to  the  male  parent  in  this 
part  and  to  the  female  parent  in  that ;  so,  during  the  forma- 
tion of  reproductive  cells,  there  will  arise  in  one  a  predomi- 
nance of  the  physiological  units  derived  from  the  father,  and 
in  another  a  predominance  of  the  physiological  units  derived 
from  the  mother.  Thus,  then,  every  fertilized  germ,  be- 
sides containing  different  amounts  of  the  two  parental  influ- 
ences, will  contain  different  kinds  of  influences — this  having 
received  a  marked  impress  from  one  grandparent,  and  that 
from  another.  Without  further  exposition  the  reader  will 
see  how  this  cause  of  complication,  running  back  through 
each  line  of  ancestry,  must  produce  in  every  germ  numerous 
minute  differences  among  the  units. 

Here,  then,  we  have  a  clue  to  the  multiplied  variations, 
and  sometimes  extreme  variations,  that  arise  in  races  which 
have  once  begun  to  vary.  Amid  countless  different  combina- 
tions of  units  derived  from  parents,  and  through  them  from 
ancestors,  immediate  and  remote — amid  the  various  conflicts 
in  their  slightly-different  organic  polarities,  opposing  and 
conspiring  with  one  another  in  all  ways  and  degrees;  there 
will  from  time  to  time  arise  special  proportions  causing 
special  deviations.  From  the  general  law  of  probabilities  it 
may  be  concluded  that  while  these  involved  influences,  derived 
from  many  progenitors,  must,  on  the  average  of  cases,  ob- 
scure and  partially  neutralize  one  another;  there  must  occa- 
sionally result  such  combinations  of  them  as  will  produce 
considerable  divergences  from  average  structures;  and,  at 
rare  intervals,  such  combinations  as  will  produce  very  marked 
divergences.  There  is  thus  a  correspondence  between  the 
inferable  results  and  the  results  as  habitually  witnessed. 

§  90.  Still  there  remains  a  difficulty.    It  may  be  said  that 


VARIATION.  333 

admitting  functional  change  to  be  the  initiator  of  variation 
— granting  that  the  physiological  units  of  an  organism  long 
subject  to  new  conditions,  will  tend  to  become  modified  in 
such  way  as  to  cause  change  of  structure  in  offspring;  yet 
there  will  still  be  no  cause  of  the  supposed  heterogeneity 
among  the  physiological  units  of  different  individuals.  There 
seems  validity  in  the  objection,  that  as  all  the  members  of 
a  species  whose  circumstances  have  been  altered  will  be  affected 
in  the  same  manner,  the  results,  when  they  begin  to  show 
themselves  in  descendants,  will  show  themselves  in  the  same 
manner:  not  multiform  variations  will  arise,  but  deviations 
all  in  one  direction. 

The  reply  is  simple.  The  members  of  a  species  thus  cir- 
cumstanced will  not  be  similarly  affected.  In  the  absence  of 
absolute  uniformity  among  them,  the  functional  changes 
caused  in  them  will  be  more  or  less  dissimilar.  Just  as  men 
of  slightly-unlike  dispositions  behave  in  quite  opposite  ways 
under  the  same  circumstances;  or  just  as  men  of  slightly- 
unlike  constitutions  get  diverse  disorders  from  the  same 
cause,  and  are  diversely  acted  on  by  the  same  medicine;  so, 
the  insensibly-differentiated  members  of  a  species  whose  con- 
ditions have  been  changed,  may  at  once  begin  to  undergo 
various  kinds  of  functional  changes.  As  we  have  already 
seen,  small  initial  contrasts  may  lead  to  large  terminal  con- 
trasts. The  intenser  cold  of  the  climate  into  which  a  species 
has  migrated,  may  cause  in  one  individual  increased  con- 
sumption of  food  to  balance  the  greater  loss  of  heat;  while 
in  another  individual  the  requirement  may  be  met  by  a 
thicker  growth  of  fur.  Or,  when  meeting  with  the  new  foods 
which  a  new  region  furnishes,  accident  may  determine  one 
member  of  the  species  to  begin  with  one  kind  and  another 
member  with  another  kind;  and  hence  may  arise  established 
habits  in  these  respective  members  and  their  descendants. 
Xow  when  the  functional  divergences  thus  set  up  in  sundry 
families  of  a  species  have  lasted  long  enough  to  affect  their 
constitutions,  and  to  modify  somewhat  the  physiological  units 


334:  THE  INDUCTIONS  OF  BIOLOGY. 

thrown  off  in  their  reproductive  cells,  the  divergences  pro- 
duced by  these  in  offspring  will  be  of  divers  kinds.  And 
the  original  homogeneity  of  constitution  having  been  thus 
destroyed,  variation  may  go  on  with  increasing  facility. 
There  will  result  a  heterogeneous  mixture  of  modifications  of 
structure  caused  by  modifications  of  function;  and  of  still 
more  numerous  correlated  modifications,  indirectly  so  caused. 
By  natural  selection  of  the  most  divergent  forms,  the  unlike- 
nesses  of  parents  will  be  rendered  more  marked,  and  the 
limits  of  variation  wider.  Until  at  length  the  divergences  of 
constitutions  and  modes  of  life,  become  great  enough  to  lead 
to  segregation  of  the  varieties. 

§  91.  That  variations  must  occur,  and  that  they  must  ever 
tend,  both  directly  and  indirectly,  towards  adaptive  modifica- 
tions, are  conclusions  deducible  from  first  principles;  apart 
from  any  detailed  interpretations  like  the  above.  That  the 
state  of  homogeneity  is  an  unstable  state  we  have  found  to 
be  a  universal  truth.  Each  species  must  pass  from  the  uni- 
form into  the  more  or  less  multiform,  unless  the  incidence  of 
external  forces  is  exactly  the  same  for  all  its  members,  which 
it  never  can  be.  Through  the  process  of  differentiation  and 
integration,  which  of  necessity  brings  together,  or  keeps  to- 
gether, like  individuals,  and  separates  unlike  ones  from  them, 
there  must  nevertheless  be  maintained  a  tolerably  uniform 
species,  so  long  as  there  continues  a  tolerably  uniform  set  of 
conditions  in  which  it  may  exist.  But  if  the  conditions 
change,  either  absolutely  by  some  disturbance  of  the  habitat 
or  relatively  by  spread  of  the  species  into  other  habitats,  then 
the  divergent  individuals  that  result  must  be  segregated 
by  the  divergent  sets  of  conditions  into  distinct  varieties 
(First  Principles,  §  166).  When,  instead  of  contemplating 
a  species  in  the  aggregate,  we  confine  our  attention  to  a 
single  member  and  its  descendants,  we  see  it  to  be  a  corollary 
from  the  general  law  of  equilibration  that  the  moving  equili- 
brium constituted  by  the  vital  actions  in  each  member  of 


VARIATION.  335 

tliis  family,  must  remain  constant  8O  long  as  the  external 
actions  to  which  they  cor-espond  remain  constant;  and  that 
if  the  external  actions  aro  changed,  the  disturbed  balance  of 
internal  changes,  if  not  overthrown,  cannot  cease  undergoing 
modification  until  the  internal  changes  are  again  in  equi- 
librium with  the  external  actions:  corresponding  structural 
alterations  having  arisen. 

On  passing  from  these  derivative  laws  to  the  ultimate  law, 
we  see  that  Variation  is  necessitated  by  the  persistence  of  force. 
The  members  of  a  species  inhabiting  any  area  cannot  be  sub- 
ject to  like  sets  of  forces  over  the  whole  of  that  area.  And 
if,  in  different  parts  of  the  area,  different  kinds  or  amounts  or 
combinations  of  forces  act  on  them,  they  cannot  but  become 
different  in  themselves  and  in  their  progeny.  To  say  other- 
wise, is  to  say  that  differences  in  the  forces  will  not  produce 
differences  in  the  effects ;  which  is  to  deny  the  persistence  of 
force. 


CHAPTER  X. 

GENESIS,    HEREDITY,     AND     VARIATION1". 

§  92.  A  QUESTION  raised,  and  hypothetical!}-  answered,  in 
§§78  and  79,  was  there  postponed"  until  we  had  dealt  with 
the  topics  of  Heredity  and  Variation.  Let  us  now  resume 
the  consideration  of  this  question,  in  connexion  with  sundry 
others  which  the  facts  suggest. 

After  contemplating  the  several  methods  by  which  the 
multiplication  of  organisms  is  carried  on — after  ranging  them 
under  the  two  heads  of  Homogenesis,  in  which  the  succes- 
sive generations  are  similarly  produced,  and  Heterogenesis, 
in  which  they  are  dissimilarly  produced — after  observing  that 
Homogenesis  is  nearly  always  sexual  genesis,  while  Heteroge- 
nesis is  asexual  genesis  with  occasionally-recurring  sexual 
genesis;  we  came  to  the  questions — why  is  it  that  some  or- 
ganisms multiply  in  the  one  way  and  some  in  the  other? 
and  why  is  it  that  where  agamogenesis  prevails  it  is  usually, 
from  time  to  time,  interrupted  by  gamogenesis  ?  In  seeking 
answers  to  these  questions,  we  inquired  whether  there  are 
common  to  both  Homogenesis  and  Heterogenesis,  any  condi- 
tions under  which  alone  sperm-cells  and  germ-cells  arise  and 
are  united  for  the  production  of  new  organisms;  and  we 
reached  the  conclusion  that,  in  all  cases,  they  arise  only 
when  there  is  an  approach  to  equilibrium  between  the  forces 
which  produce  growth  and  the  forces  which  oppose  growth. 
This  answer  to  the  question — when  does  gamogenesis  recur? 
336 


GENESIS,  HEREDITY,   AND  VARIATION.  337 

still  left  unanswered  the  question — why  does  gamogenesis 
recur  ?  And  to  this  the  reply  suggested  was,  that  the  ap- 
proach towards  general  equilibrium  in  organisms,  "  is  ac- 
companied by  an  approach  towards  molecular  equilibrium  in 
them;  and  that  the  need  for  this  union  of  sperm-cell  with 
germ-cell  is  the  need  for  overthrowing  this  equilibrium,  and 
re-establishing  active  molecular  change  in  the  detached  germ 
— a  result  probably  effected  by  mixing  the  slightly-different 
physiological  units  of  slightly-different  individuals."  This  is 
the  hypothesis  which  we  have  now  to  consider.  Let  us  first 
look  at  the  evidences  which  certain  inorganic  phenomena 
furnish. 

The  molecules  of  any  aggregate  which  have  not  a  balanced 
arrangement,  inevitably  tend  towards  a  balanced  arrangement. 
As  before  mentioned  (First  Principles,  §  100),  amorphous 
wrought  iron,  when  subject  to  continuous  jar,  begins  to  arrange 
itself  into  crystals — its  atoms  assume  a  condition  of  polar 
equilibrium.  The  particles  of  unannealed  glass,  which  are  so 
unstably  arranged  that  slight  disturbing  forces  make  them 
separate  into  small  groups,  take  advantage  of  that  greater 
freedom  of  movement  given  by  a  raised  temperature,  to  ad- 
just themselves  into  a  state  of  relative  rest.  During  any 
such  re-arrangement  the  aggregate  exercises  a  coercive  force 
over  its  units.  Just  as  in  a  growing  crystal  the  atoms  suc- 
cessively assimilated  from  the  solution,  are  made  by  the 
already  crystallized  atoms  to  take  a  certain  form,  and  even  to 
re-complete  that  form  when  it  is  broken;  so  in  any  mass  of 
unstably-arranged  atoms  which  passes  into  a  stable  arrange- 
ment, each  atom  conforms  to  the  forces  exercised  on  it  by  all 
the  other  atoms.  This  is  a  corollary  from  the  general  law  of 
equilibration.  We  saw  (First  Principles,  §  170)  that  every 
change  is  towards  equilibrium;  and  that  change  can  never 
cease  until  equilibrium  is  reached.  Organisms,  above 

all  other  aggregates,  conspicuously  display  this  progressive 
equilibration;  because  their  units  are  of  such  kinds,  and  so 
conditioned,  as  to  admit  of  easy  re-arrangement.  Those 


338  THE  INDUCTIONS  OP  BIOLOGY. 

extremely  active  changes  which  go  on  during  the  early 
stages  of  evolution,  imply  an  immense  excess  of  the  mole- 
cular forces  over  those  antagonist  forces  which  the  aggregate 
exercises  on  the  molecules.  While  this  excess  continues,  it 
is  expended  in  growth,  development,  and  function:  expendi- 
ture for  any  of  these  purposes  being  proof  that  part  of  the 
force  constituting  molecular  tensions  remains  unbalanced. 
Eventually,  however,  this  excess  diminishes.  Either,  as  in 
organisms  which  do  not  expend  much  energy,  decrease  of 
assimilation  leads  to  its  decline;  or,  as  in  organisms  which 
expend  much  energy,  it  is  counterbalanced  by  the  rapidly- 
increasing  reactions  of  the  aggregate  (§46).  The  cessation 
of  growth  when  followed,  as  in  some  organisms,  by  death, 
implies  the  arrival  at  an  equilibrium  between  the  molecular 
forces  and  those  forces  which  the  aggregate  opposes  to  them. 
When,  as  in  other  organisms,  growth  ends  in  the  establish- 
ment of  a  moving  equilibrium,  there  is  implied  such  a 
decreased  preponderance  of  the  molecular  forces,  as  leaves 
no  surplus  beyond  that  which  is  used  up  in  functions.  The 
declining  functional  activity  characteristic  of  advancing  life, 
expresses  a  further  decline  in  this  surplus.  And  when 
all  vital  movements  come  to  an  end,  the  implication  is 
that  the  actions  of  the  units  on  the  aggregate  and  the 
reactions  of  the  aggregate  on  the  units  are  completely 
balanced.  Hence,  while  a  state  of  rapid  growth  indi- 

cates such  a  play  of  forces  among  the  units  of  an  aggregate 
as  will  produce  active  re-distribution,  the  diminution  and 
arrest  of  growth  shows  that  the  units  have  fallen  into  such 
relative  positions  that  re-distribution  is  no  longer  so  facile. 
When,  therefore,  we  see  that  gamogenesis  recurs  only  when 
growth  is  decreasing,  or  has  come  to  an  end,  we  must  say 
that  it  recurs  only  when  the  organic  units  are  approximating 
to  equilibrium — only  when  their  mutual  restraints  prevent 
them  from  readily  changing  their  arrangements  in  obedience 
to  incident  forces. 

That  units  of  like  forms  can  be  built  up  into  a  more  stable 


GENESIS,   HEREDITY,  AND  VARIATION.  339 

aggregate  than  units  of  slightly  unlike  forms,  is  tolerably 
manifest  a  priori.  And  we  have  facts  which  prove  that 
mixing  allied  but  somewhat  different  units;  does  lead  to  com- 
parative instability.  Most  metallic  alloys  exemplify  this 
truth.  Common  solder,  which  is  a  mixture  of  lead  and  tin, 
melts  at  a  much  lower  temperature  than  either  lead  or  tin. 
The  compound  of  lead,  tin,  and  bismuth,  called  "  fusible 
metal/'  becomes  fluid  at  the  temperature  of  boiling  water; 
while  the  temperatures  at  which  lead,  tin,  and  bismuth  be- 
come fluid  are,  respectively,  612°,  44*2°,  and  497°  F.  Still 
more  remarkable  is  the  illustration  furnished  by  potassium 
and  sodium.  These  metals  are  very  near  akin  in  all  respects 
— in  their  specific  gravities,  their  atomic  weights,  their 
chemical  affinities,  and  the  properties  of  their  compounds. 
That  is  to  say,  all  the  evidences  unite  to  show  that  their 
units,  though  not  identical,  have  a  close  resemblance.  What 
now  happens  when  they  are  mixed?  Potassium  alone  melts 
at  136°,  sodium  alone  melts  at  190°,  but  the  alloy  of  potassium 
and  sodium  is  liquid  at  the  ordinary  temperature  of  the  air. 
Observe  the  meaning  of  these  facts,  expressed  in  general  terms. 
The  maintenance  of  a  solid  form  by  any  group  of  units  implies 
among  them  an  arrangement  so  stable  that  it  is  not  over- 
thrown by  the  incident  forces.  Whereas  the  assumption  of  a 
liquid  form  implies  that  the  incident  forces  suffice  to  destroy 
the  arrangement  of  the  units.  In  the  one  case  the  thermal 
undulations  fail  to  dislocate  the  parts;  while  in  the  other 
case  the  parts  are  so  dislocated  by  the  thermal  undulations 
that  they  fall  into  total  disorder — a  disorder  admitting  of  easy 
re-arrangement  into  any  other  order.  For  the  liquid  state  is 
a  state  in  which  the  units  become  so  far  free  from  mutual 
restraints,  that  incident  forces  can  change  their  relative  posi- 
tions very  readily.  Thus  we  have  reason  to  conclude  that  an 
aggregate  of  units  which,  though  in  the  main  similar  to  one 
another,  have  minor  differences,  must  be  more  unstable  than 
an  aggregate  of  homogeneous  units.  The  one  will  yield  to 
disturbing  forces  which  the  other  successfully  resists. 


340  THE  INDUCTIONS  OF  BIOLOGY. 

Now  though  the  colloidal  molecules  of  which  organisms 
are  mainly  built,  are  themselves  highly  composite;  and 
though  the  physiological  units  compounded  out  of  these  col- 
loidal molecules  must  have  structures  far  more  involved; 
yet  it  must  happen  with  such  units,  as  with  simple  units, 
that  those  which  have  exactly  like  forms  will  admit  of  ar- 
rangement into  a  more  stable  aggregate  than  those  which 
have  slightly-unlike  forms.  Among  units  of  this  order,  as 
among  units  of  a  simpler  v,rder,  imperfect  similarity  must 
entail  imperfect  balance  in  anything  formed  of  them,  and 
consequent  diminished  ability  to  withstand  disturbing  forces. 
Hence,  given  two  organisms  which,  by  diminished  nutrition  or 
increased  expenditure,  are  being  arrested  in  their  growths — 
given  in  each  an  approaching  equilibrium  between  the  forces 
of  the  units  and  the  forces  of  the  aggregate — given,  that 
is,  such  a  comparatively  balanced  state  among  the  units  that 
re-arrangement  of  them  by  incident  forces  is  no  longer  so 
easy;  and  it  will  follow  that  by  uniting  a  group  of  units 
from  the  one  organism  with  a  group  of  slightly-different 
units  from  the  other,  the  tendency  towards  equilibrium  will 
be  diminished,  and  the  mixed  units  will  be  rendered  more 
modifiable  in  their  arrangements  by  the  forces  acting  on 
them:  they  will  be  so  far  freed  as  to  become  again  capable 
of  that  re-distribution  which  constitutes  evolution. 

And  now  let  us  test  this  hypothesis  by  seeing  what  power 
it  gives  us  of  interpreting  established  inductions. 

§  93.  The  majority  of  plants  being  hermaphrodites,  it  has, 
until  quite  recently,  been  supposed  that  the  ovules  of  each 
flower  are  fertilized  by  pollen  from  the  anthers  of  the  same 
flower.  Mr.  Darwin,  however,  has  shown  that  the  arrange- 
ments are  generally  such  as  to  prevent  this.  Either  the  ovules 
and  the  pollen  are  not  ripe  simultaneously,  or  obstacles  pre- 
vent access  of  the  one  to  the  other.  At  the  same  time  he  has 
shown  that  there  exist  arrangements,  often  of  a  remarkable 
kind,  which  facilitate  the  transfer  of  pollen  by  insects  from  the 


GENESIS,   HEREDITY,   AND  VARIATION.  341 

stamens  of  one  flower  to  the  pistil  of  another.  Simi- 

larly, it  has  been  found  that  among  the  lower  animals,  herma- 
phrodism  does  not  usually  involve  the  production  of  fertile 
ova  by  the  union  of  sperm-cells  and  germ-cells  developed  in 
the  same  individual;  but  that  the  reproductive  centres  of 
one  individual  are  united  with  those  of  another  to  produce 
fertile  ova.  Either,  as  in  Pyrosoma,  Perophora,  and  in  many 
higher  molluscs,  the  ova  and  spermatozoa  are  matured  at 
different  times ;  or,  as  in  annelids,  they  are  prevented  by  their 
relative  positions  from  coming  in  contact. 

Remembering  the  fact  that  among  the  higher  classes  of 
organisms,  fertilization  is  always  effected  by  combining  the 
sperm-cell  of  one  individual  with  the  germ-cell  of  another; 
and  joining  with  it  the  above  fact  that  among  hermaphrodite 
organisms,  the  germ-cells  developed  in  any  individual  are 
usually  not  fertilized  by  sperm-cells  developed  in  the  same 
individual;  we  see  reason  for  thinking  that  the  essential 
thing  in  fertilization,  is  the  union  of  specially-fitted  portions 
of  different  organisms.  If  fertilization  depended  on  the 
peculiar  properties  of  sperm-cell  and  germ-cell,  as  such ;  then, 
in  hermaphrodite  organisms,  it  would  be  a  matter  of  indiffer- 
ence whether  the  united  sperm-cells  and  germ-cells  were 
those  of  the  same  individual  or  those  of  different  individuals. 
But  the  circumstance  that  there  exist  in  such  organisms 
elaborate  appliances  for  mutual  fertilization,  shows  that  un- 
likeness  of  derivation  in  the  united  reproductive  centres,  is 
the  desideratum.  Now  this  is  just  what  the  foregoing 

hypothesis  implies.  If,  as  was  concluded,  fertilization  has 
for  its  object  the  disturbance  of  that  approaching  equilibrium 
existing  among  the  physiological  units  separated  from  an 
adult  organism ;  and  if,  as  we  saw  reason  to  think,  this  object 
is  effected  by  mixture  with  the  slightly-different  physiologi- 
cal units  of  another  organism;  then,  we  at  the  same  time  see 
that  this  object  will  not  be  effected  by  mixture  with  physio- 
logical units  belonging  to  the  same  organism.  Thus,  the  hypo- 
thesis leads  us  to  expect  such  provisions  as  we  find. 
23 


342  THE  INDUCTIONS  OP  BIOLOGY. 

§  94.  But  here  a  difficulty  presents  itself.  These  proposi- 
tions seem  to  involve  the  conclusion  that  self-fertilization  is 
impossible.  It  apparently  follows  from  them,  that  a  group  of 
physiological  units  from  one  part  of  an  organism  ought  to 
have  no  power  of  altering  the  state  of  approaching  balance  in 
a  group  from  another  part  of  it.  Yet  self-fertilization  does 
occur.  Though  the  ovules  of  one  plant  are  generally  fer- 
tilized by  pollen  from  another  plant  of  the  same  kind,  yet 
they  may  be,  some  of  them,  fertilized  by  pollen  of  the  same 
plant ;  and,  indeed,  there  are  plants  in  which  self-fertilization 
is  the  rule :  even  provision  being  in  some  cases  made  to  pre- 
vent fertilization  by  pollen  from  other  individuals.  And 
though,  among  hermaphrodite  animals,  self-fertilization  is 
usually  negatived  by  structural  or  functional  arrangements, 
yet  in  certain  Entozoa  there  appear  to  be  special  provisions 
by  which  the  sperm-cells  and  the  germ-cells  of  the  same  indi- 
vidual may  be  united,  when  not  previously  united  with  those 
of  another  individual.  Nay,  it  has  even  been  shown  that  in 
certain  Ascidians  the  contents  of  oviduct  and  spermiduct  of 
the  same  individual  produce,  when  united,  fertile  ova  whence 
evolve  perfect  individuals.  Certainly,  at  first  sight,  these 
facts  do  not  consist  with  the  above  supposition.  Neverthe- 
less there  is  something  like  a  solution. 

In  the  last  chapter,  when  considering  the  variations  caused 
in  offspring  from  uniting  elements  representing  unlike 
parental  constitutions,  it  was  pointed  out  that  in  an  unfolding 
organism,  composed  of  slightly-different  physiological  units 
derived  from  slightly-different  parents,  there  cannot  be  main- 
tained an  even  distribution  of  the  two  orders  of  units.  We 
saw  that  the  instability  of  the  homogeneous  negatives  the 
uniform  blending  of  them ;  and  that,  by  the  process  of  differ- 
entiation and  integration,  they  must  be  more  or  less  separated ; 
so  that  in  one  part  of  the  body  the  influence  of  one  parent 
will  predominate,  and  in  another  part  of  the  body  the  influe- 
ence  of  the  other  parent:  an  inference  which  harmonizes 
with  daily  observation.  We  also  saw  that  the  sperm-cells  or 


GENESIS,    HEREDITY,   AND  VARIATION.  343 

germ-cells  produced  by  such  an  organism  must,  in  virtue  of 
these  same  laws,  be  more  or  less  unlike  one  another.  It  was 
shown  that  through  segregation,  some  of  the  sperm-cells  or 
germ-cells  will  get  an  excess  of  the  physiological  units  derived 
from  one  side,  and  some  of  them  an  excess  of  those  derived 
from  the  other  side :  a  cause  which  accounts  for  the  unlike- 
nesses  among  offspring  simultaneously  produced.  Now  from 
this  segregation  of  the  different  orders  of  physiological  units, 
inherited  from  different  parents  and  lines  of  ancestry,  there 
arises  the  possibility  of  self-fertilization  in  hermaphrodite 
organisms.  If  the  physiological  units  contained  in  the  sperm- 
cells  and  germ-cells  of  the  same  flower,  are  not  quite  homo- 
geneous— if  in  some  of  the  ovules  the  physiological  units 
derived  from  the  one  parent  greatly  predominate,  and  in  some 
of  the  ovules  those  derived  from  the  other  parent ;  and  if  the 
like  is  true  of  the  pollen-cells;  then,  some  of  the  ovules  may 
be  nearly  as  much  contrasted  with  some  of  the  pollen-cells  in 
the  characters  of  their  contained  units,  as  were  the  ovules  and 
pollen-cells  of  the  parents  from  which  the  plant  proceeded. 
Between  part  of  the  sperm-cells  and  part  of  the  germ-cells, 
the  community  of  nature  will  be  such  that  fertilization  will 
not  result  from  their  union;  but  between  some  of  them, 
the  differences  of  constitution  will  be  such  that  their  union 
will  produce  the  requisite  molecular  instability.  The  facts, 
so  far  as  they  are  known,  seem  in  harmony  with  this  deduc- 
tion. Self-fertilization  in  flowers,  when  it  takes  place,  is  not 
so  efficient  as  mutual  fertilization.  Though  some  of  the 
ovules  produce  seeds,  yet  more  of  them  than  usual  are  abor- 
tive. From  which,  indeed,  results  the  establishment  of  varie- 
ties that  have  structures  favourable  to  mutual  fertilization; 
since,  being  more  prolific,  these  have,  other  things  equal, 
greater  chances  in  the  "  struggle  for  existence." 

Further  evidence  is  at  hand  supporting  this  interpreta- 
tion. There  is  reason  to  believe  that  self-fertilization,  which 
at  the  best  is  comparatively  inefficient,  loses  all  efficiency  in 
course  of  time.  After  giving  an  account  of  the  provisions  for 


344:  THE  INDUCTIONS  OP  BIOLOGY. 

an  occasional,  or  a  frequent,  or  a  constant  crossing  between 
flowers;  and  after  quoting  Prof.  Huxley  to  the  effect  that 
among  hermaphrodite  animals,  there  is  no  case  in  which  "  the 
occasional  influence  of  a  distinct  individual  can  be  shown  to 
be  physically  impossible ;  "  Mr.  Darwin  writes — "  from  these 
several  considerations  and  from  the  many  special  facts  which 
I  have  collected,  but  which  I  am  not  here  able  to  give,  I  am 
strongly  inclined  to  suspect  that,  both  in  the  vegetable  and 
animal  kingdoms,  an  occasional  intercross  with  a  distinct  in- 
dividual is  a  law  of  nature in  none,  as  I  suspect, 

can  self-fertilization  go  on  for  perpetuity."  This  conclusion, 
based  wholly  on  observed  facts,  is  just  the  conclusion  to  which 
the  foregoing  argument  points.  That  necessary  action  and 
the  re-action  between  the  parts  of  an  organism  and  the 
organism  as  a  whole — that  power  of  an  aggregate  to  re-mould 
the  units,  which  is  the  correlative  of  the  power  of  the  units  to 
build  up  into  such  an  aggregate ;  implies  that  any  differences 
existing  among  the  units  inherited  by  an  organism,  must 
gradually  diminish.  Being  subject  in  common  to  the  total 
forces  of  the  organism,  they  will  in  common  be  modified  to- 
wards congruity  with  these  forces,  and  therefore  towards  like- 
ness with  one  another.  If,  then,  in  a  self-fertilizing  organism 
and  its  self-fertilizing  descendants,  such  contrasts  as  origi- 
nally existed  among  the  physiological  units  are  progressively 
obliterated — if,  consequently,  there  can  no  longer  be  a  segre- 
gation of  different  physiological  units  in  different  sperm- 
cells  and  germ-cells;  self-fertilization  will  become  impos- 
sible. Step  by  step  the  fertility  will  diminish,  and  the  series 
will  finally  die  out. 

And  now  observe,  in  confirmation  of  this  view,  that  self- 
fertilization  is  limited  to  organisms  in  which  an  approximate 
equilibrium  among  the  organic  forces  is  not  long  maintained. 
While  growth  is  actively  going  on,  and  the  physiological  units 
are  subject  to  a  continually-changing  distribution  of  forces, 
no  decided  assimilation  of  the  units  can  be  expected :  like 
forces  acting  on  the  unlike  units  will  tend  to  segregate  them, 


GENESIS,   HEREDITY,   AND  VARIATION.  345 

so  long  as  continuance  of  evolution  permits  further  segrega- 
tion; and  only  when  further  segregation  cannot  go  on,  will 
the  like  forces  tend  to  assimilate  the  units.  Hence,  where 
there  is  no  prolonged  maintenance  of  an  approximate  organic 
balance,  self-fertilization  may  be  possible  for  some  gener- 
ations; but  it  will  be  impossible  in  organisms  distinguished 
by  a  sustained  moving  equilibrium. 

§  95.  The  interpretation  which  it  affords  of  sundry  pheno- 
mena familiar  to  breeders  of  animals,  adds  probability  to  the 
hypothesis.  Mr.  Darwin  has  collected  a  large  "  body  of  facts, 
showing,  in  accordance  with  the  almost  universal  belief  of 
breeders,  that  with  animals  and  plants  a  cross  between  dif- 
ferent varieties,  or  between  individuals  of  the  same  variety 
but  of  another  strain,  gives  vigour  and  fertility  to  the  off- 
spring; and  on  the  other  hand,  that  close  interbreeding  di- 
minishes vigour  and  fertility," — a  conclusion  harmonizing 
with  the  current  belief  respecting  family-intermarriages  in 
the  human  race.  Have  we  not  here  a  solution  of  these  facts  ? 
Relations  must,  on  the  average  of  cases,  be  individuals  whose 
physiological  units  are  more  nearly  alike  than  usual.  Ani- 
mals of  different  varieties  must  be  those  whose  physiological 
units  are  more  unlike  than  usual.  In  the  one  case,  the  un- 
likeness  of  the  units  may  frequently  be  insufficient  to  pro- 
duce fertilization;  or,  if  sufficient  to  produce  fertilization,  not 
sufficient  to  produce  that  active  molecular  change  required 
for  vigorous  development.  In  the  other  case,  both  fertiliza- 
tion and  vigorous  development  will  be  made  probable. 

Nor  are  we  without  a  cause  for  the  irregular  manifestations 
of  these  general  tendencies.  The  mixed  physiological  units 
composing  any  organism  being,  as  we  have  seen,  more  or  less 
segregated  in  the  reproductive  centres  it  throws  off;  there 
may  arise  various  results  according  to  the  degrees  of  difference 
among  the  units,  and  the  degrees  in  which  the  units  are  segre- 
gated. Of  two  cousins  who  have  married,  the  common  grand- 
parents may  have  had  either  similar  or  dissimilar  constitu- 


346  THE  INDUCTIONS  OF  BIOLOGY. 

tions;  and  if  their  constitutions  were  dissimilar,  the  proba- 
bility that  their  married  grandchildren  will  have  offspring  will 
be  greater  than  if  their  constitutions  were  similar.  Or  the 
brothers  and  sisters  from  whom  these  cousins  descended,  in- 
stead of  severally  inheriting  the  constitutions  of  their  parents 
in  tolerably  equal  degrees,  may  have  severally  inherited  them 
in  very  different  degrees :  in  which  last  case,  intermarriages 
among  the  cousins  will  be  less  likely  to  prove  infertile.  Or 
the  brothers  and  sisters  from  whom  these  cousins  descended, 
may  severally  have  married  persons  very  like,  or  very 
unlike,  themselves;  and  from  this  cause  there  may  have 
resulted,  either  an  undue  likeness,  or  a  due  unlikeness, 
between  the  married  cousins.*  These  several  causes,  con- 
spiring and  conflicting  in  endless  ways  and  degrees,  will 
work  multiform  effects.  Moreover,  differences  of  segrega- 
tion will  make  the  reproductive  centres  produced  by  the 
same  nearly-related  organisms,  vary  considerably  in  their 
amounts  of  unlikeness;  and  therefore,  supposing  their 
amounts  of  unlikeness  great  enough  to  cause  fertilization,  this 
*  I  omitted  to  name  here  a  cause  which  may  be  still  more  potent  in  pro- 
ducing irregularity  in  the  results  of  cousin-marriages.  So  far  as  I  can  learn, 
no  attempt  has  been  made  to  d:stinguish  between  such  results  as  arise  when 
the  related  parents  from  whom  the  cousins  descend  are  of  the  same  sex  and 
those  which  arise  when  they  are  of  different  sexes.  In  the  one  case  two 
sisters  have  children  who  intermarry ;  and  in  the  other  case  a  brother  and 
a  sister  have  children  who  intermarry.  The  marriages  of  cousins  in  these 
two  cases  may  be  quite  dissimilar  in  their  results.  If  there  is  a  tendency 
to  limitation  of  heredity  by  sex — if  daughters  usually  inherit  more  from  the 
mother  than  sons  do,  while  sons  inherit  more  from  the  father  than  from  the 
mother,  then  two  sisters  will  on  the  average  of  cases  be  more  alike  in  con- 
stitution than  a  sister  and  a  brother.  Consequently  the  descendants  of  two 
sisters  will  differ  less  in  their  constitutions  than  the  descendants  of  a  brother 
and  a  sister ;  and  marriage  in  the  first  case  will  be  more  likely  to  prove  in- 
jurious from  absence  of  dissimilarity  in  the  physiological  units  than  marriage 
in  the  second.  My  own  small  circle  of  friends  furnishes  evidence  tending 
to  verify  this  conclusion.  In  one  instance  two  cousins  who  intermarried  are 
children  of  two  sisters,  and  they  have  no  offspring.  In  another  the  cousins 
who  intermarried  are  children  of  two  brothers,  and  they  have  no  offspring. 
In  the  third  case  the  cousins  were  descendants  of  two  brothers  and  only  one 
child  resulted. 


GENESIS,   HEREDITY,   AND  VARIATION.  347 

fertilization  will  be  effective  in  various  degrees.  Hence  it  may 
happen  that  among  offspring  of  nearly-related  parents,  there 
may  be  some  in  which  the  want  of  vigour  is  not  marked,  and 
others  in  which  there  is  decided  want  of  vigour.  So  that  we 
are  alike  shown  why  in-and-in  breeding  tends  to  diminish  both 
fertility  and  vigour :  and  why  the  effect  cannot  be  a  uniform 
effect,  but  only  an  average  effect. 

§  96.  While,  if  the  foregoing  arguments  are  valid,  gamo- 
genesis  has  for  its  main  result  the  initiation  of  a  new  develop- 
ment by  the  overthrow  of  that  approximate  equilibrium 
arrived  at  among  the  molecules  of  the  parent-organisms,  a  fur- 
ther result  appears  to  be  subserved  by  it.  Those  inferior  or- 
ganisms which  habitually  multiply  by  agamogenesis,  have  con- 
ditions of  life  that  are  simple  and  uniform;  while  those 
organisms  which  have  highly-complex  and  variable  conditions 
of  life,  habitually  multiply  by  gamogenesis.  Now  if  a  species 
has  complex  and  variable  conditions  of  life,  its  members  must 
be  severally  exposed  to  sets  of  conditions  that  are  slightly 
different :  the  aggregates  of  incident  forces  cannot  be  alike 
for  all  the  scattered  individuals.  Hence,  as  functional 
deviation  must  ever  be  inducing  structural  deviation,  each 
individual  throughout  the  area  occupied  tends  to  become 
fitted  for  the  particular  habits  which  its  particular  conditions 
necessitate;  and  in  so  far,  wnfitted  for  the  average  habits 
proper  to  the  species.  But  these  undue  specializations  are 
continually  checked  by  gamogenesis.  As  Mr.  Darwin  remarks, 
"  intercrossing  plays  a  very  important  part  in  nature  in 
keeping  the  individuals  of  the  same  species,  or  of  the  variety, 
true  and  uniform  in  character : "  the  idiosyncratic  divergences 
obliterate  one  another.  Gamogenesis,  then,  is  a  means  of 
turning  to  positive  advantage  the  individual  differentiations 
which,  in  its  absence,  would  result  in  positive  disadvantage. 
Were  it  not  that  individuals  are  ever  being  made  unlike  one 
another  by  their  unlike  conditions,  there  would  not  arise  in 
them  those  contrasts  of  molecular  constitution,  which  we  have 


348  THE  INDUCTIONS  OF  BIOLOGY. 

seen  to  be  needful  for  producing  the  fertilized  germs  of  new 
individuals.  And  were  not  these  individual  differentiations 
ever  being  mutually  cancelled,  they  would  end  in  a  fatal 
narrowness  of  adaptation. 

This  truth  will  be  most  clearly  seen  if  we  reduce  it  to  its 
purely  abstract  form,  thus: — Suppose  a  quite  homogeneous 
species,  placed  in  quite  homogeneous  conditions ;  and  suppose 
the  constitutions  of  all  its  members  in  complete  concord  with 
their  absolutely-uniform  and  constant  conditions ;  what  must 
happen?  The  species,  individually  and  collectively,  is  in  a 
state  of  perfect  moving  equilibrium.  All  disturbing  forces 
have  been  eliminated.  There  remains  no  force  which  can,  in 
any  way,  change  the  state  of  this  moving  equilibrium ;  either 
in  the  species  as  a  whole  or  in  its  members.  But  we  have 
seen  (First  Principles,  §  173)  that  a  moving  equilibrium  is 
but  a  transition  towards  complete  equilibration,  or  death.  The 
absence  of  differential  or  un-equilibrated  forces  among  the 
members  of  a  species,  is  the  absence  of  all  forces  which  can 
cause  changes  in  the  conditions  of  its  members — is  the  ab- 
sence of  all  forces  which  can  initiate  new  organisms.  To 
say,  as  above,  that  complete  molecular  homogeneity  existing 
among  the  members  of  a  species,  must  render  impossible  that 
mutual  molecular  disturbance  which  constitutes  fertilization, 
is  but  another  way  of  saying  that  the  actions  and  re-actions 
of  each  organism,  being  in  perfect  balance  with  the  actions 
and  re-actions  of  the  environment  upon  it,  there  remains  in 
each  organism  no  force  by  which  it  differs  from  any  other 
— no  force  which  any  other  does  not  meet  with  an  equal 
force — no  force  which  can  set  up  a  new  evolution  among  the 
units  of  any  other. 

And  so  we  reach  the  remarkable  conclusion  that  the  life  of 
a  species,  like  the  life  of  an  individual,  is  maintained  by  the 
unequal  and  ever-varying  actions  of  incident  forces  on  its 
different  parts.*  An  individual  homogeneous  throughout,  and 

*  A  propot  of  this  sentence  one  of  my  critics  writes  : — "  I  cannot  find  in 
this  book  the  statement  as  first  made  that  the  '  life  of  an  individual  is  main- 


GENESIS,   HEREDITY,  AND  VARIATION.  349 

having  its  substance  everywhere  continuously  subject  to  like 
actions,  could  undergo  none  of  those  changes  which  life  con- 
sists of;  and  similarly,  an  absolutely-uniform  species,  having 
all  its  members  exposed  to  identical  influences,  would  be 
deprived  of  that  initiator  of  change  which  maintains  its  exist- 
ence as  a  species.  Just  as,  in  each  organism,  incident  forces 
constantly  produce  divergences  from  the  mean  state  in  various 
directions,  which  are  constantly  balanced  by  opposite  diver- 
gences indirectly  produced  by /other  incident  forces;  and  just 
as  the  combination  of  rhythmical  functions  thus  maintained, 
constitutes  the  life  of  the  organism;  so,  in  a  species,  there 
is,  through  gamogenesis,  a  perpetual  neutralization  of  those 
contrary  deviations  .from  the  mean  state  which  are  caused  in 
its  different  parts  by  different  sets  of  incident  forces;  and  it 
is  similarly  by  the  rhythmical  production  and  compensation 
of  these  contrary  deviations,  that  the  species  continues  to 
live.  The  moving  equilibrium  in  a  species,  like  the  moving 
equilibrium  in  an  individual,  would  rapidly  end  in  complete 

tained  by  the  unequal  and  ever-varying  actions  of  incident  forces  on  its  dif- 
ferent parts.'  Recent  physiological  work  offers  a  startling  example  of  the 
statement." 

To  the  question  contained  in  the  first  sentence  the  answer  is  that  I  have 
not  made  the  statement  in  the  above  words,  but  that  it  is  implied  in  the  chap- 
ter entitled  "  The  Degree  of  Life  varies  as  the  Degree  of  Correspondence,"  and 
more  especially  in  §  36,  which,  towards  its  close,  definitely  involves  the  state- 
ment. The  verifying  evidence  my  critic  gives  me  is  this : — 

"  Prof.  Sherrington  has  shown  that  if  the  sensory  roots  of  the  spinal  nerves 
are  cut  one  by  one  there  is  at  first  no  general  effect  produced.  That  is  to  say, 
the  remainder  of  the  nervous  system  continues  to  function  as  before.  This 
condition  (lack  of  general  effect)  persists  until  about  six  pairs  have  been  cut. 
With  the  severance  of  the  seventh  pair,  however,  the  whole  central  nervous 
system  ceases  to  function,  so  that  stimulation  of  intact  sensory  nerves  pro- 
duces no  reflex  action.  After  a  variable  period,  but  one  of  many  hours  dura- 
tion, the  power  of  functioning  is  recovered.  That  is  to  say,  if  the  sensory 
impulses  (from  the  skin,  &c.)  reaching  the  central  nervous  system  are  rapidly 
reduced  in  amount,  there  comes  a  point  where  those  remaining  do  not  suffice 
to  keep  the  structure  'awake.'  After  a  time,  however,  it  adjusts  itself  to 
work  with  the  diminished  supply.  Similarly  Strumpell  describes  the  case  of 
a  boy  '  whose  sensory  inlets  were  all  paralyzed  except  one  eye  and  one  ear.' 
When  these  were  closed  he  instantly  fell  asleep." 


350  THE  INDUCTIONS  OF  BIOLOGY. 

equilibration,  or  death,  were  not  its  continually-dissipated 
forces  continually  re-supplied  from  without.  Besides  owing 
to  the  external  world  those  energies  which,  from  moment  to 
moment,  keep  up  the  lives  of  its  individual  members,  every 
species  owes  to  certain  more  indirect  actions  of  the  external 
world,  those  energies  which  enable  it  to  perpetuate  itself  in 
successive  generations. 

§  97.  What  evidence  still  remains  may  be  conveniently 
woven  up  along  with  a  recapitulation  of  the  argument  pursued 
through  the  last  three  chapters.  Let  us  contemplate  the  facts 
in  their  synthetic  order. 

That  compounding  and  re-compounding  through  which  we 
pass  from  the  simplest  inorganic  substances  to  the  most  com- 
plex organic  substances,  has  several  concomitants.  Each  suc- 
cessive stage  of  composition  presents  us  with  molecules  that 
are  severally  larger  or  more  integrated,  that  are  severally 
more  heterogeneous,  that  are  severally  more  unstable,  and  that 
are  more  numerous  in  their  kinds  (First  Principles,  §  151). 
And  when  we  come  to  the  substances  of  which  living  bodies 
are  formed,  we  find  ourselves  among  innumerable  divergent 
groups  and  sub-groups  of  compounds,  the  units  of  which  are 
large,  heterogeneous,  and  unstable,  in  high  degrees.  There  is 
no  reason  to  assume  that  this  process  ends  with  the  forma- 
tion of  those  complex  colloids  which  constitute  organic  matter. 
A  more  probable  assumption  is  that  out  of  the  complex  col- 
loidal molecules  there  are  evolved,  by  a  still  further  integra- 
tion, molecules  which  are  still  more  heterogeneous,  and  of 
kinds  which  are  still  more  multitudinous.  What  must  be 
their  properties?  Already  the  colloidal  molecules  are  ex- 
tremely unstable — capable  of  being  variously  modified  in 
their  characters  by  very  slight  incident  forces;  and  already 
the  complexity  of  their  polarities  prevents  them  from 
readily  falling  into  such  positions  of  equilibrium  as  results  in 
crystallization.  Now  the  organic  molecules  composed  of 
these  colloidal  molecules,  must  be  similarly  characterized  in 


GENESIS,    HEREDITY,   AND  VARIATION.  351 

far  higher  degrees.  Far  more  numerous  must  be  the  minute 
changes  that  can  be  wrought  in  them  by  minute  external 
forces;  far  more  free  must  they  remain  for  a  long  time  to 
obey  forces  tending  to  re-distribute  them;  and  far  greater 
must  be  the  number  of  their  kinds. 

Setting  out  with  these  physiological  units,  the  existence  of 
which  various  organic  phenomena  compel  us  to  recognize,  and 
the  production  of  which  the  general  law  of  Evolution  thus 
leads  us  to  anticipate;  we  get  an  insight  into  the  phenomena 
of  Genesis,  Heredity,  and  Variation.  If  each  organism  is  built 
of  certain  of  these  highly-plastic  units  peculiar  to  its  species 
— units  which  slowly  work  towards  an  equilibrium  of  their 
complex  proclivities,  in  producing  an  aggregate  of  the  specific 
structure,  and  which  are  at  the  same  time  slowly  modifiable 
by  the  re-actions  of  this  aggregate — we  see  why  the  multi- 
plication of  organisms  proceeds  in  the  several  ways,  and  with 
the  various  results,  which  naturalists  have  observed. 

Heredity,  as  shown  not  only  in  the  repetition  of  the  specific 
structure  but  in  the  repetition  of  ancestral  deviations  from  it, 
becomes  a  matter  of  course ;  and  it  falls  into  unison  with  the 
fact  that,  in  various  inferior  organisms,  lost  parts  can  be 
replaced,  and  that,  in  still  lower  organisms,  a  fragment  can 
develop  into  a  whole. 

While  an  aggregate  of  physiological  units  continues  to 
grow  by  the  assimilation  of  matter  which  it  moulds  into 
other  units  of  like  type;  and  while  it  continues  to  undergo 
changes  of  structure;  no  equilibrium  can  be  arrived  at  be- 
tween the  whole  and  its  parts.  Under  these  conditions,  then, 
an  un-differentiated  portion  of  the  aggregate — a  group  of 
physiological  units  not  bound  up  into  a  specialized  tissue — 
will  be  able  to  arrange  itself  into  the  structure  peculiar  to  the 
species;  and  will  so  arrange  itself,  if  freed  from  controlling 
forces  and  placed  in  fit  conditions  of  nutrition  and  temper- 
ature. Hence  the  continuance  of  agamogenesis  in  little- 
differentiated  organisms,  so  long  as  assimilation  continues  to 
be  greatly  in  excess  of  expenditure. 


352  THE  INDUCTIONS  OP  BIOLOGY. 

But  let  growth  be  checked  and  development  approach  its 
completion — let  the  units  of  the  aggregate  be  severally  ex- 
posed to  an  almost  constant  distribution  of  forces;  and  they 
must  begin  to  equilibrate  themselves.  Arranged,  as  they  will 
gradually  be,  into  comparatively  stable  attitudes  in  relation 
to  one  another,  their  mobility  will  diminish;  and  groups  of 
them,  partially  or  wholly  detached,  will  no  longer  readily  re- 
arrange themselves  into  the  specific  form.  Agamogenesis  will 
be  no  longer  possible ;  or,  if  possible,  will  be  no  longer  easy. 

When  we  remember  that  the  force  which  keeps  the  Earth 
in  its  orbit  is  the  gravitation  of  each  particle  in  the  Earth 
towards  every  one  of  the  group  of  particles  existing  92,000,000 
of  miles  off;  we  cannot  reasonably  doubt  that  each  unit  in 
an  organism  acts  on  all  the  other  units,  and  is  reacted  on  bv 
them:  not  by  gravitation  only  but  chiefly  by  other  energies. 
When,  too,  we  learn  that  glass  has  its  molecular  constitution 
changed  by  light,  and  that  substances  so  rigid  and  stable  as 
metals  have  their  atoms  re-arranged  by  forces  radiated  in 
the  dark  from  adjacent  objects ;  *  we  are  obliged  to  conclude 
that  the  excessively-unstable  units  of  which  organisms  are 
built,  must  be  sensitive  in  a  transcendant  degree  to  all  the 
forces  pervading  the  organisms  composed  of  them — must  be 
tending  ever  to  re-adjust,  not  only  their  relative  attitudes 
but  their  molecular  structures,  into  equilibrium  with  these 
forces.  Hence,  if  aggregates  of  the  same  species  are  differ- 
ently conditioned,  and  re-act  differently  on  their  component 
units,  their  component  units  will  be  rendered  somewhat  dif- 
ferent; and  they  will  become  the  more  different  the  more 
widely  the  re-actions  of  the  aggregates  upon  them  differ,  and 
the  greater  the  number  of  generations  through  which  these 
different  re-actions  of  the  aggregates  upon  them  are  continued. 

*  Fifty  years  before  the  discovery  of  the  Rontgen  rays  and  those  habitually 
emanating  from  uranium,  it  had  been  observed  by  Moser  that  under  certain 
conditions  the  surfaces  of  metals  receive  permanent  impressions  from  appro- 
priate objects  placed  upon  them.  Such  facts  show  that  the  molecules  of  sub- 
stances propagate  in  all  directions  special  ethereal  undulations  determined  by 
their  special  constitutions. 


GENESIS,    HEREDITY,   AND  VARIATION.  353 

If,  then,  unlikenesses  of  function  among  individuals  of  the 
same  species,  produce  unlikenesses  between  the  physiological 
units  of  one  individual  and  those  of  another,  it  becomes  com- 
prehensible that  when  groups  of  units  derived  from  two  indi- 
viduals are  united,  the  group  formed  will  be  more  unstable 
than  either  of  the  groups  was  before  their  union.  The  mixed 
units  will  be  less  able  to  resist  those  re-distributing  forces 
which  cause  evolution;  and  may  thus  have  restored  to  them 
the  capacity  for  development  which  they  had  lost. 

This  view  harmonizes  with  the  conclusion,  which  we  saw 
reason  to  draw,  that  fertilization  does  not  depend  on  any 
intrinsic  peculiarities  of  sperm-cells  and  germ-cells,  but  de- 
pends on  their  derivation  from  different  individuals.  It 
explains  the  facts  that  nearly-related  individuals  are  less  likely 
to  have  offspring  than  others,  and  that  their  offspring,  when 
they  have  them,  are  frequently  feeble.  And  it  gives  us  a  key 
to  the  converse  fact  that  the  crossing  of  varieties  results  in 
unusual  vigour. 

Bearing  in  mind  that  the  slightly-different  orders  of  phy- 
siological units  which  an  organism  inherits  from  its  parents, 
are  subject  to  the  same  set  of  forces,  and  that  when  the 
organism  is  fully  developed  this  set  of  forces,  becoming  con- 
stant, tends  slowly  to  re-mould  the  two  orders  of  units  into 
the  same  form;  we  see  how  it  happens  that  self-fertilization 
becomes  impossible  in  the  higher  organisms,  while  it  remains 
possible  in  the  lower  organisms.  In  long-lived  creatures  which 
have  tolerably-definite  limits  of  growth,  this  assimilation  of 
the  somewhat-unlike  physiological  units  is  liable  to  go  on  to 
an  appreciable  extent;  whereas  in  organisms  which  do  not 
continuously  subject  their  component  units  to  constant  forces, 
there  will  be  much  less  of  this  assimilation.  And  where  the 
assimilation  is  not  considerable,  the  segregation  of  mixed 
units  may  cause  the  sperm-cells  and  germ-cells  developed  in 
the  same  individual,  to  be  sufficiently  different  to  produce,  by 
their  union,  fertile  germs;  and  several  generations  of  self- 
fertilizing  descendants  may  succeed  one  another,  before  the 


354  THE  INDUCTIONS  OF   BIOLOGY. 

two  orders  of  units  have  had  their  unlikenesses  so  far  dimin- 
ished that  they  will  no  longer  do  this.  The  same  principles 
explain  for  us  the  variable  results  of  union  between  nearly- 
related  organisms.  According  to  the  contrasts  among  the 
physiological  units  they  inherit  from  parents  and  ancestors; 
according  to  the  unlike  proportions  of  the  contrasted  units 
which  they  severally  inherit;  and  according  to  the  degrees 
of  segregation  of  such  units  in  different  sperm-cells  and 
germ-cells;  it  may  happen  that  two  kindred  individuals  will 
produce  the  ordinary  number  of  offspring  or  will  produce 
none;  or  will  at  one  time  be  fertile  and  at  another  not;  or 
will  at  one  time  have  offspring  of  tolerable  strength  and  at 
another  time  feeble  offspring. 

To  the  like  causes  are  also  ascribable  the  phenomena  of 
Variation.  These  are  unobtrusive  while  the  tolerably-uni- 
form conditions  of  a  species  maintain  tolerable  uniformity 
among  the  physiological  units  of  its  members;  but  they  be- 
come obtrusive  when  differences  of  conditiohs,  entailing  con- 
siderable functional  differences,  have  entailed  decided  differ- 
ences among  the  physiological  units,  and  when  the  different 
physiological  units,  differently  mingled  in  every  individual, 
come  to  be  variously  segregated  and  variously  combined. 

Did  space  permit,  it  might  be  shown  that  this  hypothesis 
is  a  key  to  many  further  facts — to  the  fact  that  mixed  races 
are  comparatively  plastic  under  new  conditions;  to  the  fact 
that  pure  races  show  predominant  influences  in  the  offspring 
when  crossed  with  mixed  races ;  to  the  fact  that  while  mixed 
breeds  are  often  of  larger  growth,  pure  breeds  are  the  more 
hardy — have  functions  less-easily  thrown  out  of  balance. 
But  without  further  argument  it  will,  I  think,  be  admitted 
that  the  power  of  this  hypothesis  to  explain  so  many  pheno- 
mena, and  to  bring  under  a  common  bond  phenomena  which 
seem  so  little  allied,  is  strong  evidence  of  its  truth.  And 
such  evidence  gains  greatly  in  strength  on  observing  that 
this  hypothesis  brings  the  facts  of  Genesis,  Heredity,  and 
Variation  into  harmony  with  first  principles.  We  see  that 


GENESIS,   HEREDITY,  AND  VARIATION.  355 

these  plastic  physiological  units,  which  we  find  ourselves 
obliged  to  assume,  are  just  such  more  integrated,  more  hete- 
rogeneous, more  unstable,  and  more  multiform  molecules,  as 
would  result  from  continuance  of  the  steps  through  which 
organic  matter  is  reached.  We  see  that  the  differentia- 
tions of  them  assumed  to  occur  in  differently-conditioned 
aggregates,  and  the  equilibrations  of  them  assumed  to  occur 
in  aggregates  which  maintain  constant  conditions,  are  but 
corollaries  from  those  universal  principles  implied  by  the 
persistence  of  force.  We  see  that  the  maintenance  of  life 
in  the  successive  generations  of  a  species,  becomes  a  con- 
sequence of  the  continual  incidence  of  new  forces  on  the 
species,  to  replace  the  forces  that  are  ever  being  rhythmically 
equilibrated  in  the  propagation  of  the  species.  And  we 
thus  see  that  these  apparently-exceptional  phenomena  dis- 
played in  the  multiplication  of  organic  beings,  fall  into  their 
places  as  results  of  the  general  laws  of  Evolution.  We  have, 
therefore,  weighty  reasons  for  entertaining  the  hypothesis 
which  affords  us  this  interpretation. 


CHAPTER  X\ 

GENESIS,    HEREDITY,    AND    VARIATION 
CONCLUDED. 

§  97 a.  SINCE  the  foregoing  four  chapters  were  written, 
thirty-four  years  ago,  the  topics  with  which  they  deal  have 
been  widely  discussed  and  many  views  propounded.  Ancient 
hypotheses  have  been  abandoned,  and  other  hypotheses,  re- 
ferring tacitly  or  avowedly  to  the  cell-doctrine,  have  been 
set  forth.  Before  proceeding  it  will  be  well  to  describe  the 
chief  among  these. 

Most  if  not  all  of  them  proceed  on  the  assumption,  shown 
in  §  66  to  be  needful,  that  the  structural  characters  of  organ- 
isms are  determined  by  the  special  natures  of  units  which  are 
intermediate  between  the  chemical  units  and  the  morphologi- 
cal units — between  the  invisible  molecules  of  proteid-sub- 
stances  and  the  visible  tissue-components  called  cells. 

Four  years  after  the  first  edition  of  this  volume  was 
published,  appeared  Mr.  Darwin's  work,  The  Variation  of 
Animals  and  Plants  under  Domestication;  and  in  this  he  set 
forth  his  doctrine  of  Pangenesis.  Referring  to  the  doctrine 
of  physiological  units  which  the  preceding  chapters  work  out, 
he  at  first  expressed  a  doubt  whether  his  own  was  or  was  not 
the  same,  but  finally  concluded  that  it  was  different.  He  was 
right  in  so  concluding.  Throughout  my  argument  the  im- 
plication everywhere  is  that  the  physiological  units  are  all 
of  one  kind;  whereas  Mr.  Darwin  regards  his  component 
units,  or  "  gemmules,"  as  being  of  innumerable  unlike  kinds. 
He  supposes  that  every  cell  of  every  tissue  gives  off  gemmules 
356 


GENESIS,  HEREDITY,   AND  VARIATION.  357 

special  to  itself,  and  capable  of  developing  into  similar  cells. 
We  may  here,  in  passing,  note  that  this  view  implies  a  funda- 
mental distinction  between  unicellular  organisms  and  the 
component  cells  of  multicellular  organisms,  which  are  other- 
wise homologous  with  them.  For  while  in  their  essential 
structures,  their  essential  internal  changes,  and  their  essential 
processes  of  division,  the  Protozoa  and  the  component  units 
of  the  Metazoa  are  alike,  the  doctrine  of  Pangenesis  implies 
that  though  the  units  when  separate  do  not  give  off  invisible 
gemmules  the  grouped  units  do. 

Much  more  recently  have  been  enunciated  the  hypotheses 
of  Prof.  Weismann,  differing  from  the  foregoing  hypotheses 
in  two  respects.  In  the  first  place  it  is  assumed  that  the  frag- 
ment of  matter  out  of  which  each  organism  arises  consists  of 
two  portions — one  of  them,  the  germ-plasm,  reserved  within 
the  generative  organ  of  the  incipient  individual,  representing 
in  its  components  the  structure  of  the  species,  and  gives  origin 
to  the  germs  of  future  individuals;  and  the  other  of  them, 
similarly  representative  of  the  specific  structure,  giving  origin 
to  the  rest  of  the  body,  or  soma,  but  contains  in  its  compo- 
nents none  of  those  latent  powers  possessed  by  those  of  the 
germ-plasm.  In  the  second  place  the  germ-plasm,  in  com- 
mon with  the  soma-plasm,  consists  of  multitudinous  kinds 
of  units  portioned  out  to  originate  the  various  organs.  Of 
these  there  are  groups,  sub-groups,  and  sub-sub-groups. 
The  largest  of  them,  called  "  idants,"  are  supposed  each  to 
contain  a  number  of  "  ids  "  ;  within  each  id  there  are  numer- 
ous "  determinants  "  ;  and  each  determinant  is  made  up  of 
many  "  biophors  " — the  smallest  elements  possessing  vitality. 
Passing  over  details,  the  essential  assumption  is  that  there 
exists  a  separate  determinant  for  each  part  of  the  organ- 
ism capable  of  independent  variation;  and  Prof.  Weismann 
infers  that  while  there  may  be  but  one  for  the  blood  and 
but  one  .for  a  considerable  area  of  skin  (as  a  stripe  of  the 
zebra)  there  must  be  a  determinant  for  each  scale  on  a  butter- 
fly's wing:  the  number  on  the  four  wings  being  over  two 
24 


358  THE  INDUCTIONS  OP  BIOLOGY. 

hundred  thousand.  And  then  each  cluster  of  biophors  com- 
posing a  determinant  has  to  find  its  way  to  the  place  where 
there  is  to  be  formed  the  part  it  represents. 

Here  it  is  needless  to  specify  the  modifications  of  these 
hypotheses  espoused  by  various  biologists — all  of  them  assum- 
ing that  the  structural  traits  of  each  species  are  expressed 
in  certain  units  intermediate  between  morphological  units  and 
chemical  units. 

§  97&.  A  true  theory  of  heredity  must  be  one  which  recog- 
nizes the  relevant  phenomena  displayed  by  all  classes  of 
organism.  We  cannot  assume  two  kinds  of  heredity,  one 
for  plants  and  another  for  animals.  Hence  a  theory  of 
heredity  may  be  first  tested  by  observing  whether  it  is  equally 
applicable  to  both  kingdoms  of  living  things.  Genesis,  he- 
redity, and  variation,  as  seen  in  plants,  are  simpler  and  more 
accessible  than  as  seen  in  animals.  Let  us  then  note  what 
these  imply. 

Already  in  §  77  I  have  illustrated  the  power  which  some 
plants  possess  of  developing  new  individuals  from  mere  frag- 
ments of  leaves  and  even  from  detached  scales.  Striking 
as  are  the  facts  there  instanced,  they  are  scarcely  more 
significant  than  some  which  are  familiar.  The  formation  of 
cauline  buds,  presently  growing  into  shoots,  shows  us  a  kind 
of  inheritance  which  a  true  theory  must  explain.  As  de- 
scribed by  Kerner,  such  buds  arise  in  Pimpernel,  Toad-flax, 
etc.,  below  the  seed-leaves,  even  while  yet  there  are  no  axils 
in  which  buds  usually  grow;  and  in  many  plants  they  arise 
from  intermediate  places  on  the  stem :  that  is,  without  defi- 
nite relations  to  pre-existing  structures.  How  fortuitous 
is  their  origin  is  shown  when  a  branch  is  induced  to  bud  by 
keeping  it  wrapped  round  with  a  wet  cloth.  Even  still  better 
proved  is  the  absence  of  any  relation  between  cauline  buds 
and  normal  germs  by  the  frequent  growth  of  them  out  of 
"  callus  " — the  tissue  which  spreads  over  wounds  and  the  cut 
ends  of  -branches.  It  is.  not  easy  to  reconcile  these  facts 


GENESIS,   HEREDITY,   AND  VARIATION.  359 

with  Mr.  Darwin's  hypothesis  of  gemmules.  We  have  to 
assume  that  where  a  cauline  bud  emerges  there  are  present 
in  due  proportions  gemmules  of  all  the  parts  which  will  pres- 
ently arise  from  it — leaves,  stipules,  bracts,  petals,  stamens, 
anthers,  etc.  We  have  to  assume  this  though,  at  the  time 
the  bud  originates,  sundry  of  these  organs,  as  the  parts  of 
flowers,  do  not  exist  on  the  plant  or  tree.  And  we  have  to 
assume  that  the  gemmules  of  such  parts  are  duly  provided 
in  a  portion  of  adventitious  callus,  far  away  from  the  normal 
places  of  fructification.  Moreover,  the  resulting  shoot  may 
or  may  not  produce  all  the  parts  which  the  gemmules  repre- 
sent; and  when,  perhaps  after  years,  flowers  are  produced 
on  its  side  shoots,  there  must  exist  at  each  point  the  needful 
proportion  of  the  required  gemmules ;  though  there  have  been 
no  cells  continually  giving  them  off. 

Still  less  does  the  hypothesis  of  Prof.  Weismann  harmonize 
with  the  evidence  as  plants  display  it.  Plant-embryogeny 
yields  no  sign  of  separation  between  germ-plasm  and  soma- 
plasm;  and,  indeed,  the  absence  of  such  separation  is  ad- 
mitted. After  instancing  cases  among  certain  of  the  lower 
animals,  in  which  no  differentiation  of  the  two  arises  in  the 
first  generation  resulting  from  a  fertilized  ovum,  Prof.  Weis- 
mann continues : — 

"The  same  is  true  as  regards  the  higher  plants,  in  which  the  first 
shoot  arising  from  the  seed  never  contains  germ-cells,  or  even  cells 
which  subsequently  become  differentiated  into  germ  cells.  In  all 
these  last-mentioned  cases  the  germ-cells  are  not  present  in  the  first 
person  arising  by  embryogeny  as  special  cells,  but  are  only  formed  in 
much  later  cell-generations  from  the  offspring  of  certain  cells  of  which 
this  first  person  was  composed.  (Germ-Plasm,  p.  185.) 

How  this  admission  consists  with  the  general  theory  it  is 
difficult  to  understand.  The  units  of  the  soma-plasm  are 
here  recognized  as  having  the  same  generative  powers  as 
the  units  of  the  germ-plasm.  In  so  far  as  one  organic 
kingdom  and  a  considerable  part  of  the  other  are  concerned 
the  doctrine  is  relinquished.  Eelinquishment  is,  indeed, 
necessitated  even  by  the  ordinary  facts,  and  still  more  by  the 


360  THE  INDUCTIONS  OF  BIOLOGY. 

facts  just  instanced.  Defence  of  it  involves  the  assertion 
that  where  buds  arise,  normal  or  cauline,  there  exist  in  due 
proportion  the  various  ids  with  their  contained  determinants 
— that  these  are  diffused  throughout  the  growing  part  of  the 
soma ;  and  this  implies  that  the  somatic  tissue  does  not  differ 
in  generative  power  from  the  germ-plasm. 

The  hypothesis  of  physiological  units,  then,  remains  out- 
standing. For  cauline  buds  imply  that  throughout  the  plant- 
tissue,  where  not  unduly  differentiated,  the  local  physiological 
units  have  a  power  of  arranging  themselves  into  the  structure 
of  the  species. 

But  this  hypothesis,  too,  as  it  now  stands,  is  inadequate. 
Under  the  form  thus  far  given  to  it,  it  fails  to  explain  some 
accompanying  facts.  For  if  the  branch  just  instanced  as 
producing  a  cauline  bud  be  cut  off  and  its  end  stuck  in  the 
ground,  or  if  it  be  bent  down  and  a  portion  of  it  covered 
with  earth,  there  will  grow  from  it  rootlets  and  presently 
roots.  The  same  portion  of  tissue  which  otherwise  would 
have  produced  a  shoot  with  all  its  appendages,  constituting  an 
individual,  now  produces  only  a  special  part  of  an  individual. 

§  97c.  Certain  kindred  facts  of  animal  development  may 
now  be  considered.  Similar  insufficiencies  are  disclosed. 

The  often-cited  reproduction  of  a  crab's  lost  claw  or  a 
lizard's  tail,  Mr.  Darwin  thought  explicable  by  his  hypo- 
thesis of  diffused  gemmules,  representing  all  organs  or  their 
component  cells.  But  though,  after  simple  amputation,  re- 
growth  of  the  proximate  part  of  the  tail  is  conceivable  as 
hence  resulting,  it  is  not  easy  to  understand  how  the  remoter 
part,  the  components  of  which  are  now  absent  from  the 
organism,  can  arise  afresh  from  gemmules  no  longer  origin- 
ated in  due  proportion.  Prof.  Weismann's  hypothesis,  again, 
implies  that  there  must  exist  at  the  place  of  separation,  a 
ready-provided  supply  of  determinants,  previously  latent, 
able  to  reproduce  the  missing  tail  in  all  its  details — nay, 
even  to  do  this  several  times  over :  a  strong  supposition ! 


GENESIS,   HEREDITY,   AND  VARIATION.  361 

The  hypothesis  of  physiological  units,  as  set  forth  in  preced- 
ing chapters,  appears  less  incompetent:  reproduction  of  the 
lost  part  would  seem  to  be  a  normal  result  of  the  proclivity 
towards  the  form  of  the  entire  organism.  But  now  what  are 
we  to  say  when,  instead  of  being  cut  off  transversely,  the 
tail  is  divided  longitudinally  and  each  half  becomes  a  com- 
plete tail?  What  are  we  to  say  when,  if  these  two  tails  are 
similarly  dealt  with,  the  halves  again  complete  themselves; 
and  so  until  as  many  as  sixteen  tails  have  been  formed? 
Here  the  hypothesis  of  physiological  units  appears  to  fail 
utterly ;  for  the  tendency  it  implies  is  to  complete  the  specific 
form,  by  reproducing  a  single  tail  only. 

Various  annulose  animals  display  anomalies  of  develop- 
ment difficult  to  explain  on  any  hypothesis.  We  have 
creatures  like  the  fresh-water  Nats  which,  though  it  has  ad- 
vanced structures,  including  a  vascular  system,  branchiae, 
and  a  nervous  cord  ending  with  cephalic  ganglia,  nevertheless 
shows  us  an  ability  like  that  of  the  Hydra  to  reproduce  the 
whole  from  a  small  part:  nearly  forty  pieces  into  which  a 
Nais  was  cut  having  severally  grown  into  complete  animals. 
Again  we  have,  in  the  order  Polychcetce,  types  like  Myrianida, 
in  which  by  longitudinal  budding  a  string  of  individuals, 
sometimes  numbering  even  thirty,  severally  develop  certain 
segments  into  heads,  while  increasing  their  segments  in 
number.  In  yet  other  types  there  occurs  not  longitudinal 
gemmation  only,  but  lateral  gemmation :  a  segment  will  send 
out  sideways  a  bud  which  presently  becomes  a  complete 
worm.  Once  more,  Syllis  ramosa  is  a  species  in  which  the 
individual  worms  growing  from  lateral  buds,  while  remaining 
attached  to  the  parent,  themselves  give  origin  to  buds;  and 
so  produce  a  branched  aggregate  of  worms.  How  shall  we 
explain  the  reparative  and  reproductive  powers  thus  exempli- 
fied? It  seems  undeniable  that  each  portion  has  an  ability 
to  produce,  according  to  circumstances,  the  whole  creature 
or  a  missing  part  of  the  creature.  When  we  read  of  Sir  J. 
Dalyell  that  he  "  cut  a  Dasychone  into  three  pieces ;  the 


362  THE  INDUCTIONS  OF  BIOLOGY. 

hindermost  produced  a  head,  the  anterior  piece  developed  an 
anus,  and  the  middle  portion  formed  both  a  head  and  a  tail " 
we  are  not  furnished  with  an  explanation  by  the  hypothesis 
of  gemmules  or  by  the  hypothesis  of  determinants;  for  we 
cannot  arbitrarily  assume  that  wherever  a  missing  organ  has 
to  be  produced  there  exists  the  needful  supply  of  gemmules 
or  of  determinants  representing  that  organ.  The  hypothesis 
that  physiological  units  have  everywhere  a  proclivity  towards 
the  organic  form  of  the  species,  appears  more  congruous  with 
the  facts;  but  even  this  does  not  cover  the  cases  in  which  a 
new  worm  grows  from  a  lateral  bud.  The  tendency  to  com- 
plete the  individual  structure  might  be  expected  rather  to 
restrain  this  breaking  of  the  lines  of  complete  structure. 

Still  less  explicable  in  any  way  thus  far  proposed  are 
certain  remedial  actions  seen  in  animals.  An  example  of 
them  was  furnished  in  §  67,  where  "  false  joints  "  were  de- 
scribed— joints  formed  at  places  where  the  ends  of  a  broken 
bone,  failing  to  unite,  remain  moveable  one  upon  the  other. 
According  to  the  character  of  the  habitual  motions  there 
results  a  rudely  formed  hinge-joint  or  a  ball-and-socket  joint, 
either  having  the  various  constituent  parts — periosteum, 
fibrous  tissue,  capsule,  ligaments.  Now  Mr.  Darwin's  hypo- 
thesis, contemplating  only  normal  structures,  fails  to  account 
for  this  formation  of  an  abnormal  structure.  Neither  can 
we  ascribe  this  local  development  to  determinants:  there 
were  no  appropriate  ones  in  the  germ-plasm,  since  no  such 
structure  was  provided  for.  Nor  does  the  hypothesis  of 
physiological  units,  as  presented  in  preceding  chapters,  yield 
an  interpretation.  These  could  have  no  other  tendency  than 
to  restore  the  normal  form  of  the  limb,  and  might  be  expected 
to  oppose  the  genesis  of  these  new  parts. 

Thus  we  have  to  seek,  if  not  another  hypothesis,  then  some 
such  qualification  of  an  existing  hypothesis  as  will  harmonize 
it  with  various  exceptional  phenomena. 

§  97d.  In  Part  II  of  the  Principles  of  Sociology,  published 


GENESIS,  HEREDITY,   AND  VARIATION.  363 

in  1876,  will  be  found  elaborated  in  detail  that  analogy  be- 
tween individual  organization  and  social  organization  which 
was  briefly  sketched  out  in  an  essay  on  "The  Social  Organism" 
published  in  1860.  In  §§  241-3  a  parallel  is  drawn  between 
the  developments  of  the  sustaining  systems  of  the  two;  and 
it  is  pointed  out  how,  in  the  one  case  as  in  the  other,  the  com- 
ponents— here  organic  units  and  there  citizens — have  their 
activities  and  arrangements  mainly  settled  by  local  conditions. 
One  leading  example  is  that  the  parts  constituting  the  alimen- 
tary canal,  while  jointly  fitted  to  the  nature  of  the  food,  are 
severally  adapted  to  the  successive  stages  at  which  the  food 
arrives  in  its  progress;  and  that  in  an  analogous  way  the 
industries  carried  on  by  peoples  forming  different  parts  of  a 
society,  are  primarily  determined  by  the  natures  of  things 
around — agriculture,  pastoral  and  arable,  special  manufactures 
and  minings,  ship-building  and  fishing :  the  respective  groups 
falling  into  fit  combinations  and  becoming  partially  modified 
to  suit  their  work.  The  implication  is  that  while  the  organ- 
ization of  a  society  as  a  whole  depends  on  the  characters  of 
its  units,  in  such  way  that  by  some  types  of  men  despotisms 
are  always  evolved  while  by  other  types  there  are  evolved 
forms  of  government  partially  free — forms  which  repeat 
themselves  in  colonies — there  is,  on  the  other  hand,  in  every 
case  a  local  power  of  developing  appropriate  structures.  And 
it  might  have  been  pointed  out  that  similarly  in  types  of 
creatures  not  showing  much  consolidation,  as  the  Annelida, 
many  of  the  component  divisions,  largely  independent  in 
their  vitalities,  are  but  little  affected  in  their  structures  by 
the  entire  aggregate. 

My  purpose  at  that  time  being  the  elucidation  of  socio- 
logical truths,  it  did  not  concern  me  to  carry  further  the 
biological  half  of  this  comparison.  Otherwise  there  might 
have  been  named  the  case  in  which  a  supernumerary  finger, 
beginning  to  bud  out,  completes  itself  as  a  local  organ  with 
bones,  muscles,  skin,  nail,  etc.,  in  defiance  of  central  control : 
even  repeating  itself  when  cut  off.  There  might  also  have 


364  THE  INDUCTIONS  OF  BIOLOGY. 

been  instanced  the  above-named  formation  of  a  false  joint 
with  its  appurtenances.  For  the  implication  in  both  cases  is 
that  a  local  group  of  units,  determined  by  circumstances 
towards  a  certain  structure,  coerces  its  individual  units  into 
that  structure. 

Now  let  us  contemplate  the  essential  fact  in  the  analogy. 
The  men  in  an  Australian  mining-camp,  as  M.  Pierre 
Leroy  Beaulieu  points  out,  fall  into  Anglo-Saxon  usages 
different  from  those  which  would  characterize  a  French 
mining-camp.  Emigrants  to  a  far  West  settlement  in  America 
quickly  establish  post-office,  bank,  hotel,  newspaper,  and 
other  urban  institutions.  We  are  thus  shown  that  along 
with  certain  traits  leading  to  a  general  type  of  social  organ- 
ization, there  go  traits  which  independently  produce  fit  local 
organizations.  Individuals  are  led  into  occupations  and 
official  posts,  often  quite  new  to  them,  by  the  wants  of  those 
around — are  now  influenced  and  now  coerced  into  social 
arrangements  which,  as  shown  perhaps  by  gambling  saloons, 
by  shootings  at  sight,  and  by  lynchings,  are  scarcely  at  all 
affected  by  the  central  government.  Now  the  physiological 
units  in  each  species  appear  to  have  a  similar  combination  of 
capacities.  Besides  their  general  proclivity  towards  the 
specific  organization,  they  show  us  abilities  to  organize 
themselves  locally;  and  these  abilities  are  in  some  cases  dis- 
played in  defiance  of  the  general  control,  as  in  the  super- 
numerary finger  or  the  false  joint.  Apparently  each  physio- 
logical unit,  while  having  in  a  manner  the  whole  organism 
as  the  structure  which,  along  with  the  rest,  it  tends  to  form, 
has  also  an  aptitude  to  take  part  in  forming  any  local  struc- 
ture, and  to  assume  its  place  in  that  structure  under  the 
influence  of  adjacent  physiological  units. 

A  familiar  fact  supports  this  conclusion.  Everyone  has 
at  hand,  not  figuratively  but  literally,  an  illustration.  Let 
him  compare  the  veins  on  the  backs  of  his  two  hands^  either 
with  one  another  or  with  the  veins  on  another  person's  hands, 
and  he  will  see  that  the  branchings  and  inosculations  do  not 


GENESIS,   HEREDITY,   AND   VARIATION.  305 

correspond:  there  is  no  fixed  pattern.  But  on  progressing 
inwards  from  the  extremities,  the  distribution  of  the  veins 
becomes  settled — there  is  a  pattern-arrangement  common  to 
all  persons.  These  facts  imply  a  predominating  control  by 
adjacent  parts  where  control  by  the  aggregate  is  less  easy. 
A  constant  combination  of  forces  which,  towards  the  centre, 
produces  a  typical  structure,  fails  to  do  this  at  the  periphery 
where,  during  development,  the  play  of  forces  is  less  settled. 
This  peripheral  vascular  structure,  not  having  become  fixed 
because  one  arrangement  is  as  good  as  another,  is  in  each 
determined  by  the  immediately  surrounding  influences. 

§  9? 'e.  And  now  let  us  contemplate  the  verifications  which 
recent  experiments  have  furnished — experiments  made  by 
Prof.  G.  Born  of  Breslau,  confirming  results  earlier  reached 
by  Vulpian  and  adding  more  striking  results  of  kindred 
nature.  They  leave  no  longer  doubtful  the  large  share  taken 
by  local  organizing  power  as  distinguished  from  central 
organizing  power. 

The  independent  vitality  shown  by  separated  portions  of 
ventral  skin  from  frog-larvae  may  be  named  as  the  first  illus- 
tration. With  their  attached  yolk-cells  these  lived  for  days, 
and  underwent  such  transformations  as  proved  some  struc- 
tural proclivity,  though  of  course  the  product  was  amorphous. 
Detached  portions  of  tails  of  larvae  went  on  developing  their 
component  parts  in  much  the  same  ways  as  they  would  have 
done  if  remaining  attached.  More  striking  still  was  the 
evidence  furnished  by  experiments  in  grafting.  These  proved 
that  the  undifferentiated  rudiment  of  an  organ  will,  when 
cut  off  and  joined  to  a  non-homologous  place  in  another 
individual,  develop  itself  as  it  would  have  done  if  left  in  its 
original  place.  In  brief,  then,  we  may  say  that  each  part  is 
in  chief  measure  autogenous. 

These  strange  facts  presented  by  small  aggregates  of  or- 
ganic matter,  which  are  the  seats  of  extremely  complex  forces, 
will  seem  less  incomprehensible  if  we  observe  what  has  taken 


366  THE  INDUCTIONS  OF  BIOLOGY. 

place  in  a  vast  aggregate  of  inorganic  matter  which  is  the 
seat  of  very  simple  forces — the  Solar  System.  Transcend- 
ently  different  as  this  is  in  all  other  respects,  it  is  analogous 
in  the  respect  that,  as  factors  of  local  structures,  local  influ- 
ences predominate  over  the  influences  of  the  aggregate.  For 
while  the  members  of  the  Solar  System,  considered  as  a  whole, 
are  subordinate  to  the  totality  of  its  forces,  the  arrange- 
ments in  each  part  of  it  are  produced  almost  wholly  by  the 
play  of  forces  in  that  part.  Though  the  Sun  affects  the 
motions  of  the  Moon,  and  though  during  the  evolution  of  the 
Earth-and-Moon  system  the  Sun  exercised  an  influence,  yet 
the  relations  of  our  world  and  its  satellite  in  respect  of 
masses  and  motions  were  in  the  main  locally  determined. 
Still  more  clearly  was  it  thus  with  Jupiter  and  his  satellites 
or  Saturn  with  his  rings  and  satellites.  Remembering  that 
the  ultimate  units  of  matter  of  which  the  Solar  System  is 
composed  are  of  the  same  kinds,  and  that  they  act  on  one 
another  in  conformity  with  the  same  laws,  we  see  that,  re- 
mote as  the  case  is  from  the  one  we  are  considering  in  all 
other  respects,  it  is  similar  in  the  respect  that  during  organ- 
ization the  energies  in  each  locality  work  effects  which  are 
almost  independent  of  the  effects  worked  by  the  general  ener- 
gies. In  this  vast  aggregate,  as  in  the  minute  aggregates  now 
in  question,  the  parts  are  practically  autogenous. 

Having  thus  seen  that  in  a  way  we  have  not  hitherto  recog- 
nized the  same  general  principles  pervade  inorganic  and 
organic  evolution,  let  us  revert  to  the  case  of  super-organic 
evolution  from  which  a  parallel  was  drawn  above.  As  anal- 
ogous to  the  germinal  mass  of  units  out  of  which  a  new 
organism  is  to  evolve,  let  us  take  an  assemblage  of  colonists 
not  yet  socially  organized  but  placed  in  a  fertile  region — men 
derived  from  a  society  (or  rather  a  succession  of  societies)  of 
long-established  type,  who  have  in  their  adapted  natures  the 
proclivity  towards  that  type.  In  passing  from  its  wholly 
unorganized  state  to  an  organized  state,  what  will  be  the 
first  step?  Clearly  this  assemblage,  though  it  may  have 


GENESIS,   HEREDITY,   AND  VARIATION.  367 

within  the  constitutions  of  its  units  the  potentialities  of  a 
specific  structure,  will  not  develop  forthwith  the  details  of 
that  structure.  The  inherited  natures  of  its  units  will  first 
show  themselves  by  separating  into  large  groups  devoted  to 
strongly-distinguished  occupations.  The  great  mass,  dispers- 
ing over  promising  lands,  will  make  preparations  for  farming. 
Another  considerable  portion,  prompted  by  the  general  needs, 
will  begin  to  form  a  cluster  of  habitations  and  a  trading 
centre.  Yet  a  third  group,  recognizing  the  demand  for  wood, 
alike  for  agricultural  and  building  purposes,  will  betake 
themselves  to  the  adjacent  forests.  But  in  no  case  will  the 
primary  assemblage,  before  these  separations,*  settle  the  ar- 
rangements and  actions  of  each  group :  it  will  leave  each 
group  to  settle  them  for  itself.  So,  too,  after  these  divisions 
have  arisen.  The  agricultural  division  will  not  as  a  whole 
prescribe  the  doings  of  its  members.  Spontaneous  segrega- 
tion will  occur :  some  going  to  a  pastoral  region  and  some  to 
a  tract  which  promises  good  crops.  Nor  within  each  of  these 
bodies  will  the  organization  be  dictated  by  the  whole.  The 
pastoral  group  will  separate  itself  into  clusters  who  tend 
sheep  on  the  hills  and  clusters  who  feed  cattle  on  the  plains. 
Meanwhile  those  who  have  gravitated  towards  urban  occu- 
pations will  some  of  them  make  bricks  or  quarry  stone,  while 
others  fall  into  classes  who  build  walls,  classes  who  prepare 
fittings,  classes  who  supply  furniture.  Then  along  with 
completion  of  the  houses  will  go  occupation  of  them  by  men 
who  bake  bread,  who  ma'ke  clothing,  who  sell  liquors,  and  so 
on.  Thus  each  great  group  will  go  on  organizing  itself  irre- 
spective of  the  rest;  the  sub-groups  within  each  will  do  the 
same;  and  so  will  the  sub-sub-groups.  Quite  independently 
of  the  people  on  the  hills  and  the  plains  and  in  the  town, 
those  in  the  forest  will  divide  spontaneously  into  parties  who 
cut  down  trees,  parties  who  trim  and  saw  them,  parties  who 
carry  away  the  timbers;  while  every  party  forms  for  itself 
an  organization  of  "  butty  "  or  "  boss,"  and  those  who  work 
under  him.  Similarly  with  the  ultimate  divisions — the 


368  THE  INDUCTIONS  OF  BIOLOGY. 

separate  families :  the  arrangements  and  apportionments  of 
duties  in  each  are  internally  determined.  Mark  the  fact 
which  here  chiefly  concerns  us.  This  formation  of  a  hetero- 
geneous aggregate  with  its  variously  adapted  parts,  which 
while  influenced  by  the  whole  are  mainly  self-formed,  goes 
on  among  units  of  essentially  the  same  natures,  inherited 
from  units  who  belonged  to  similar  societies.  And  now, 
carrying  this  conception  with  us,  we  may  dimly  perceive 
how,  in  a  developing  embryo,  there  may  take  place  the  form- 
ation, first  of  the  great  divisions — the  primary  layers — then 
of  the  outlines  of  systems,  then  of  component  organs,  and  so 
on  continually' with  the  minor  structures  contained  in  major 
structures;  and  how  each  of  these  progressively  smaller 
divisions  develops  its  own  organization,  irrespective  of  the 
changes  going  on  throughout  the  rest  of  the  embryo.  So 
that  though  all  parts  are  composed  of  physiological  units  of 
the  same  nature,  yet  everywhere,  in  virtue  of  local  conditions 
and  the  influence  of  its  neighbours,  each  unit  joins  in  forming 
the  particular  structure  appropriate  to  the  place.  Thus  con- 
ceiving the  matter,  we  may  in  a  vague  way  understand  the 
strange  facts  of  autogenous  development  disclosed  by  the 
above  named  experiments. 

§  97/.  "  But  how  immeasurably  complex  must  be  the 
physiological  units  which  can  behave  thus !  "  will  be  remarked 
by  the  reader.  "  To  be  able  to  play  all  parts,  alike  as  mem- 
bers of  the  whole  and  as  members  of  this  or  that  organ,  they 
must  have  an  unimaginable  variety  of  potentialities  in  their 
natures.  Each  must,  indeed,  be  almost  a  microcosm  within 
a  microcosm." 

Doubtless  this  is  true.  Still  we  have  a  consensus  of  proofs 
that  the  component  units  of  organisms  have  constitutions  of 
extremely  involved  kinds.  Contemplate  the  facts  and  their 
implications.  (1)  Here  is  some  large  division  of  the  animal 
kingdom — say  the  Vertebrata.  The  component  units  of  all 
its  members  have  certain  fundamental  traits  in  common:  all 


GENESIS,   HEREDITY,   AND  VARIATION.  369 

of  them  have  proclivities  towards  formation  of  a  vertebral 
column.  Leaving  behind  the  great  assemblage  of  Fishes  with 
its  multitudinous  types,  each  having  special  units  of  composi- 
tion, we  pass  to  the  Amphibia,  in  the  units  of  which  there 
exist  certain  traits  superposed  upon  the  traits  they  have  in 
common  with  those  of  Fishes.  Through  unknown  links  we 
ascend  to  incipient  Mammalian  types  and  then  to  developed 
Mammalian  types,  the  units  of  which  must  have  further 
superposed  traits.  Additional  traits  distinguish  the  units  of 
each  Mammalian  order;  and,  again,  those  of  every  genus 
included  in  it;  while  others  severally  characterize  the  units 
of  each  species.  Similarly  with  the  varieties  in  each  species, 
and  the  stirps  in  each  variety.  Now  the  ability  of  any  com- 
ponent unit  to  carry  within  itself  the  traits  of  the  sub-king- 
dom, class,  order,  genus,  species,  variety,  and  at  the  same 
time  to  bear  the  traits  of  immediate  ancestors,  can  exist  only 
in  a  something  having  multitudinous  proximate  elements 
arranged  in  innumerable  ways.  (2)  Again,  these  units  must 
be  at  once  in  some  respects  fixed  and  in  other  respects  plastic. 
While  their  fundamental  traits,  expressing  the  structure  of 
the  type,  must  be  unchangeable,  their  superficial  traits  must 
admit  of  modification  without  much  difficulty ;  and  the  modi- 
fied traits,  expressing  variations  in  the  parents  and  immediate 
ancestors,  though  unstable,  must  be  considered  as  capable  of 
becoming  stable  in  course  of  time.  (3)  Once  more  we  have 
to  think  of  these  physiological  units  (or  constitutional  units 
as  I  would  now  re-name  them)  as  having  such  natures  that 
while  a  minute  modification,  representing  some  small  change 
of  local  structure,  is  inoperative  on  the  proclivities  of  the 
units  throughout  the  rest  of  the  system,  it  becomes  operative 
in  the  units  which  fall  into  the  locality  where  that  change 
occurs. 

But  unimaginable  as  all  this  is,  the  facts  may  nevertheless 
in  some  way  answer  to  it.  As  before  remarked,  progressing 
science  reveals  complexity  within  complexity — tissues  made 
up  of  cells,  cells  containing  nuclei  and  cytoplasm,  cytoplasm 


370  THE  INDUCTIONS  OF  BIOLOGY. 

formed  of  a  protoplasmic  matrix  containing  granules;  and  if 
now  we  conclude  that  the  unit  of  protoplasm  is  itself  an 
inconceivably  elaborate  structure,  we  do  but  recognize  the 
complexity  as  going  still  deeper.  Further,  if  we  must  assume 
that  these  component  units  are  in  every  part  of  the  body 
acting  on  one  another  by  extremely  complicated  sets  of  forces 
(ethereal  undulations  emanating  from  each  of  the  constituent 
molecules)  determining  their  relative  positions  and  actions, 
we  are  warranted  by  the  discoveries  which  every  day  disclose 
more  of  the  marvellous  properties  of  matter.  When  to  such 
examples  as  were  given  in  §  36e  we  add  the  example  yielded 
by  recent  experiments,  showing  that  even  a  piece  of  bread, 
after  subjection  to  pressure,  exhibits  diamagnetic  properties 
unlike  those  it  previously  exhibited,  we  cannot  doubt  that 
these  complex  units  composing  living  bodies  are  all  of  them 
seats  of  energies  diffused  around,  enabling  them  to  act  and 
re-act  so  as  to  modify  one  another's  states  and  positions. 
We  are  shown,  too,  that  whatever  be  the  natures  of  the  com- 
plex forces  emanating  from  each,  it  will,  as  a  matter  of  course, 
happen  that  the  power  of  each  will  be  relatively  great  in  its 
own  neighbourhood  and  become  gradually  smaller  in  parts 
increasingly  remote:  making  more  comprehensible  the  auto- 
genous character  of  each  local  structure. 

Whatever  be  their  supposed  natures  we  are  compelled  to 
ascribe  extreme  complexity  to  these  unknown  somethings 
which  have  the  power  of  organizing  themselves  into  a  struc- 
ture of  this  or  that  species.  If  gemmules  be  alleged,  then 
the  ability  of  every  organ  and  part  of  an  organ  to  vary, 
implies  that  the  gemmules  it  gives  off  are  severally  capable 
of  receiving  minute  modifications  of  their  ordinary  struc- 
tures :  they  must  have  many  parts  admitting  of  innumerable 
relations.  Supposing  determinants  be  assumed,  then  in  ad- 
dition to  the  complexity  which  each  must  have  to  express 
in  itself  the  structure  of  the  part  evolved  from  it,  it  must 
have  the  further  complexity  implied  by  every  superposed 
modification  which  causes  a  variation  of  that  part.  And,  as 


GENESIS,   HEREDITY,   AND   VARIATION.  371 

we  have  just  seen,  the  hypothesis  of  physiological  units,  does 
not  relieve  us  from  the  need  for  kindred  suppositions. 

One  more  assumption  seems  necessary  if  we  are  to  imagine 
how  changes  of  structure  caused  by  changes  of  function  can 
be  transmitted.  Keverting  to  §  54d,  where  an  unceasing  cir- 
culation of  protoplasm  throughout  an  organism  was  inferred, 
we  must  conceive  that  the  complex  forces  of  which  each  con- 
stitutional unit  is  the  centre,  and  by  which  it  acts  on  other 
units  while  it  is  acted  on  by  them,  tend  continually  to  re- 
mould each  unit  into  congruity  with  the  structures  around: 
superposing  on  it  modifications  answering  to  the  modifica- 
tions which  have  arisen  in  those  structures.  Whence  is  to  be 
drawn  the  corollary  that  in  course  of  time  all  the  circulating 
units, — physiological,  or  constitutional  if  we  prefer  so  to  call 
them — visiting  all  parts  of  the  organism,  are  severally  made 
bearers  of  traits  expressing  local  modifications;  and  that 
those  units  which  are  eventually  gathered  into  sperm-cells 
and  germ-cells  also  bear  these  superposed  traits. 

If  against  all  this  it  be  urged  that  such  a  combination  of 
structures  and  forces  and  processes  is  inconceivably  involved, 
then  the  reply  is  that  so  astonishing  a  transformation  as 
that  which  an  unfolding  organism  displays  cannot  possibly  be 
effected  by  simple  agencies. 

§  97 g.  But  now  let  it  be  confessed  that  none  of  these  hypo- 
theses serves  to  render  the  phenomena  really  intelligible ;  and 
that  probably  no  hypothesis  which  can  be  framed  will  do  this. 
Many  problems  beyond  those  which  embryology  presents  have 
to  be  solved ;  and  no  solution  is  furnished. 

What  are  we  to  say  of  the  familiar  fact  that  certain  small 
organs  which,  with  the  approach  to  maturity,  become  active, 
entail  changes  of  structure  in  remote  parts — that  after  the 
testes  have  undergone  certain  final  developments,  the  hairs 
on  the  chin  grow  and  the  voice  deepens?  It  has  been  con- 
tended that  certain  concomitant  modifications  in  the  fluids 
throughout  the  body  may  produce  correlated  sexual  traits; 


372  THE  INDUCTIONS  OF  BIOLOGY. 

and  there  is  proof  that  in  many  of  the  lower  animals  the 
period  of  sexual  activity  is  accompanied  by  a  special  bodily 
state — sometimes  such  that  the  flesh  becomes  unwholesome 
and  even  poisonous.  But  a  change  of  this  kind  can  hardly 
account  for  a  structural  change  in  the  vocal  organs  in  Man. 
No  hypothesis  of  gemmules  or  determinants  or  physiological 
units  enables  us  to  understand  how  removal  of  the  testes 
prevents  those  developments  of  the  larynx  and  vocal  cords 
which  take  place  if  they  remain. 

The  inadequacy  of  our  explanations  we  at  once  see  in 
presence  of  a  structure  like  a  peacock's  tail-feather.  Mr. 
Darwin's  hypothesis  is  that  all  parts  of  every  organ  are  con- 
tinually giving  off  gemmules,  which  are  consequently  every- 
where present  in  their  due  proportions.  But  a  completed 
feather  is  an  inanimate  product  and,  once  formed,  can  add  to 
the  circulating  fluids  no  gemmules  representing  all  its  parts. 
If  we  follow  Prof.  Weismann  we  are  led  into  an  astounding 
supposition.  He  admits  that  every  variable  part  must  have 
a  special  determinant,  and  that  this  results  in  the  assumption 
of  over  two  hundred  thousand  for  the  four  wings  of  a  butter- 
fly. Let  us  ask  what  must  happen  in  the  case  of  a  peacock's 
feather.  On  looking  at  the  eye  near  its  end,  we  see  that  the 
minute  processes  on  the  edge  of  each  lateral  thread  must 
have  been  in  some  way  exactly  adjusted,  in  colour  and  posi- 
tion, so  as  to  fall  into  line  with  the  processes  on  adjacent 
threads :  otherwise  the  symmetrical  arrangement  of  coloured 
rings  would  be  impossible.  Each  of  these  processes,  then, 
being  an  independent  variable,  must  have  had  its  particular 
determinant.  Now  there  are  about  300  threads  on  the  shaft 
of  a  large  feather,  and  each  of  them  bears  on  the  average  1,600 
processes,  making  for  the  whole  feather  480,000  of  these  pro- 
cesses. For  one  feather  alone  there  must  have  been  480,000 
determinants,  and  for  the  whole  tail  many  millions.  And 
these,  along  with  the  determinants  for  the  detailed  parts  of 
all  the  other  feathers,  and  for  the  variable  components  of  all 
organs  forming  the  body  at  large,  must  have  been  contained 


GENESIS,   HEREDITY,   AND  VARIATION.  3^3 

t 

in  the  microscopic  head  of  a  spermatozoon !  Hardly  a  credi- 
ble supposition.  Nor  is  it  easy  to  see  how  we  are  helped  by 
the  hypothesis  of  constitutional  units.  Take  the  feather  in 
its  budding  state  and  ask  how  the  group  of  such  units,  alike 
in  structure  and  perpetually  multiplying  while  the  unfolding 
goes  on,  can  be  supposed  by  their  mutual  actions  so  to  affect 
one  another  as  eventually  to  produce  the  symmetrically-ad- 
justed processes  which  constitute  the  terminal  eye.  Imagina- 
tion, whatever  licence  may  be  given,  utterly  fails  us. 

At  last  then  we  are  obliged  to  admit  that  the  actual  organ- 
izing process  transcends  conception.  It  is  not  enough  to 
say  that  we  cannot  know  it;  we  must  say  that  we  cannot 
even  conceive  it.  And  this  is  just  the  conclusion  which 
might  have  been  drawn  before  contemplating  the  facts.  For 
if,  as  we  saw  in  the  chapter  on  "  The  Dynamic  Element  in 
Life,"  it  is  impossible  for  us  to  understand  the  nature  of  this 
element — if  even  the  ordinary  manifestations  of  it  which  a 
living  body  yields  from  moment  to  moment  are  at  bottom 
incomprehensible ;  then,  still  more  incomprehensible  must  be 
that  astonishing  manifestation  of  it  which  we  have  in  the 
initiation  and  unfolding  of  a  new  organism. 

Thus  all  we  can  do  is  to  find  some  way  of  symbolizing  the 
process  so  as  to  enable  us  most  conveniently  to  generalize  its 
phenomena ;  and  the  only  reason  for  adopting  the  hypothesis 
of  physiological  units  or  constitutional  units  is  that  it  best 
serves  this  purpose. 


25 


CHAPTER  XI. 

CLASSIFICATION. 

§  98.  THAT  orderly  arrangement  of  objects  called  Classi- 
fication has  two  purposes,  which,  though  not  absolutely 
distinct,  are  distinct  in  great  part.  It  may  be  employed  to 
facilitate  identification,  or  it  may  be  employed  to  organize 
our  knowledge.  If  a  librarian  places  his  books  in  the  alpha- 
betical succession  of  the  author's  names,  he  places  them  in 
such  way  that  any  particular  book  may  easily  be  found,  but 
not  in  such  way  that  books  of  a  given  nature  stand  together. 
When,  otherwise,  he  makes  a  distribution  of  books  according 
to  their  subjects,  he  neglects  various  superficial  similarities 
and  distinctions,  and  groups  them  according  to  certain  pri- 
mary and  secondary  and  tertiary  attributes,  which  severally 
imply  many  other  attributes — groups  them  so  that  any  one 
volume  being  inspected,  the  general  characters  of  all  the 
neighbouring  volumes  may  be  inferred.  He  puts  together 
in  one  great  division  all  works  on  History;  in  another  all 
Biographical  works;  in  another  all  works  that  treat  of 
Science ;  in  another  Voyages  and  Travels ;  and  so  on.  Each 
of  his  great  groups  he  separates  into  sub-groups;  as  when 
he  puts  different  kinds  of  Literature  under  the  heads  of 
Fiction,  Poetry,  and  the  Drama.  In  some  cases  he  makes 
sub-sub-groups;  as  when,  having  divided  his  Scientific  trea- 
tises into  abstract  and  concrete,  putting  in  the  one  Logic 
and  Mathematics  and  in  the  other  Physics,  Astronomy, 
Geology,  Chemistry,  Physiology,  &c. ;  he  goes  on  to  sub-divide 
374 


CLASSIFICATION.  375 

his  books  on  Physics,  into  those  which  treat  of  Mechanical 
Motion,  those  which  treat  of  Heat,  those  which  treat  of  Light, 
of  Electricity,  of  Magnetism. 

Between  these  two  modes  of  classification  note  the  essential 
distinctions.  Arrangement  according  to  any  single  con- 
spicuous attribute  is  comparatively  easy,  and  is  the  first  that 
suggests  itself:  a  child  may  place  books  in  the  order  of  their 
sizes,  or  according  to  the  styles  of  their  bindings.  But  ar- 
rangement according  to  combinations  of  attributes  which, 
though  fundamental,  are  not  conspicuous,  requires  analysis; 
and  does  not  suggest  itself  till  analysis  has  made  some  pro- 
gress. Even  when  aided  by  the  information  which  the 
author  gives  on  his  title  page,  it  requires  considerable  know- 
ledge to  classify  rightly  an  essay  on  Polarization;  and  in  the 
absence  of  a  title  page  it  requires  much  more  knowledge. 
Again,  classification  by  a  single  attribute,  which  the  objects 
possess  in  different  degrees,  may  be  more  or  less  serial,  or 
linear.  Books  may  be  put  in  the  order  of  their  dates,  in 
single  file;  or  if  they  are  grouped  as  works  in  one  volume, 
works  in  two  volumes,  works  in  three  volumes,  &c.,  the  groups 
may  be  placed  in  an  ascending  succession.  But  groups 
severally  formed  of  things  distinguished  by  some  common 
attribute  which  implies  many  other  attributes,  do  not  admit 
of  serial  arrangement.  You  cannot  rationally  say  either  that 
Historical  Works  should  come  before  Biographical  Works,  or 
Biographical  Works  before  Historical  Works ;  nor  of  the  sub- 
divisions of  creative  Literature,  into  Fiction,  Poetry,  and  the 
Drama,  can  you  give  a  good  reason  why  any  one  should  take 
precedence  of  the  others. 

Hence  this  grouping  of  the  like  and  separation  of  the  un- 
like which  constitutes  Classification,  can  reach  its  complete 
form  only  by  slow  steps,  I  have  shown  (Essays,  Vol.  II.,  pp. 
145-7)  that,  other  things  equal,  the  relations  among  pheno- 
mena are  recognized  in  the  order  of  their  conspicuousness ; 
and  that,  other  things  equal,  they  are  recognized  in  the  order 
of  their  simplicity.  The  first  classifications  are  sure,  there- 


376  THE  INDUCTIONS  OF  BIOLOGY. 

fore,  to  be  groupings  of  objects  which  resemble  one  another  in 
external  or  easily-perceived  attributes,  and  attributes  that  are 
not  of  complex  characters.  Those  likenesses  among  things 
which  are  due  to  their  possession  in  common  of  simple  obvious 
properties,  may  or  may  not  coexist  with  further  likenesses 
among  them.  When  geometrical  figures  are  classed  as  curvi- 
linear and  rectilinear,  or  when  the  rectilinear  are  divided 
into  trilateral,  quadrilateral,  &c.,the  distinctions  made  connote 
various  other  distinctions  with  which  they  are  necessarily 
bound  up ;  but  if  liquids  be  classed  according  to  their  visible 
characters — if  water,  alcohol,  sulphuret  of  carbon,  &c.,  be 
grouped  as  colourless  and  transparent,  we  have  things  placed 
together  which  are  unlike  in  their  essential  natures.  Thus, 
where  the  objects  classed  have  numerous  attributes,  the 
probabilities  are  that  the  early  classifications,  based  on  simple 
and  manifest  attributes,  unite  under  the  same  head  many 
objects  that  have  no  resemblance  in  the  majority  of  their 
attributes.  As  the  knowledge  of  objects  increases,  it  becomes 
possible  to  make  groups  of  which  the  members  have  more 
numerous  properties  in  common;  and  to  ascertain  what 
property,  or  combination  of  properties,  is  most  characteristic 
of  each  group.  And  the  classification  eventually  arrived  at 
is  of  such  kind  that  the  objects  in  each  group  have  more 
attributes  in  common  with  one  another  than  they  have  in 
common  with  any  excluded  objects ;  one  in  which  the  groups 
of  such  groups  are  integrated  on  the  same  principle ;  and  one 
in  which  the  degrees  of  differentiation  and  integration  are 
proportioned  to  the  degrees  of  intrinsic  unlikeness  and  like- 
ness. And  this  ultimate  classification,  while  it  serves  to  iden- 
tify the  things  completely,  serves  also  to  express  the  greatest 
amount  of  knowledge  concerning  the  things — enables  us  to 
predicate  the  greatest  number  of  facts  about  each  thing;  and 
by  so  doing  implies  the  most  precise  correspondence  between 
our  conceptions  and  the  realities. 

§  99.  Biological  classifications  illustrate  well  these  phases 


CLASSIFICATION.  377 

through  which  classifications  in  general  pass.  In  early 
attempts  to  arrange  organisms  in  some  systematic  manner, 
we  see  at  first  a  guidance  by  conspicuous  and  simple  cha- 
racters, and  a  tendency  towards  arrangement  in  linear  order. 
In  successively  later  attempts,  we  see  more  regard  paid  to 
combinations  of  characters  which  are  essential  but  often  in- 
conspicuous, and  an  abandonment  of  a  linear  arrangement  for 
an  arrangement  in  divergent  groups  and  re-divergent  sub- 
groups. 

In  the  popular  mind,  plants  are  still  classed  under  the 
heads  of  Trees,  Shrubs,  and  Herbs;  and  this  serial  classing 
according  to  the  single  attribute  of  magnitude,  swayed  the 
earliest  observers.  They  would  have  thought  it  absurd  to 
call  a  bamboo,  thirty  feet  high,  a  kind  of  grass;  and  would 
have  been  incredulous  if  told  that  the  Hart's-tongue  should 
be  placed  in  the  same  great  division  with  the  Tree-ferns. 
The  zoological  classifications  current  before  Natural  History 
became  a  science,  had  divisions  similarly  superficial  and  sim- 
ple. Beasts,  Birds,  Fishes,  and  Creeping-things  are  names 
of  groups  marked  off  from  one  another  by  conspicuous  differ- 
ences of  appearance  and  modes  of  life — creatures  that  walk 
and  run,  creatures  that  fly,  creatures  that  live  in  the  water, 
creatures  that  crawl.  And  these  groups  were  thought  of  in 
the  order  of  their  importance. 

The  first  arrangements  made  by  naturalists  were  based 
either  on  single  characters  or  on  very  simple  combinations  of 
characters;  as  that  of  Clusius,  and  afterwards  the  more 
scientific  system  of  Cesalpino,  recognizing  the  importance  of 
inconspicuous  structures.  Describing  plant-classifications, 
Lindley  says : — "  Eivinus  invented,  in  1690,  a  system  depend- 
ing upon  the  formation  of  the  corolla;  Kamel,  in  1693, 
upon  the  fruit  alone;  Magnol,  in  1720,  on  the  calyx  and 
corolla;  and  finally,  Linnaeus,  in  1731,  on  variations  in  the 
stamens  and  pistil."  In  this  last  system,  which  has  been 
for  so  long  current  as  a  means  of  identification  (regarded  by 
its  author  as  transitional),  simple  external  attributes  are 


378  THE  INDUCTIONS  OF  BIOLOGY. 

still  depended  on;  and  an  arrangement,  in  great  measure 
serial,  is  based  on  the  degrees  in  which  these  attributes  are 
possessed.  In  1703,  some  thirty  years  before  the  time  of 
Linnaeus,  our  countryman  Eay  had  sketched  the  outlines  of  a 
more  advanced  system.  He  said  that — 
Plants  are  either 

Flowerless,  or 

Flowering ;  and  these  are 
Dicotyledones,  or 
Monocotyledones. 

Among  the  minor  groups  which  he  placed  under  these  general 
heads,  "were  Fungi,  Mosses,  Ferns,  Composites,  Cichoraceae, 
Umbellifers,  Papilionaceous  plants,  Conifers,  Labiates,  &c., 
under  other  names,  but  with  limits  not  very  different  from 
those  now  assigned  to  them."  Being  much  in  advance  of  his 
age,  Bay's  ideas  remained  dormant  until  the  time  of  Jus- 
sieu;  by  whom  they  were  developed  into  what  has  become 
known  as  the  Natural  System:  a  system  subsequently  im- 
proved by  De  Candolle.  Passing  through  various  modifica- 
tions in  the  hands  of  successive  botanists,,  the  Natural  Sys- 
tem is  now  represented  by  the  following  form,  which  is 
based  upon  the  table  of  contents  prefixed  to  Vel.  II.  of  Prof. 
Oliver's  translation  of  the  Natural  History  of  Plants,  by  Prof. 
Kerner.  His  first  division,  Myxothallophyta  (=  Myxomy- 
cetes),  I  have  ventured  to  omit.  The  territory  it  occupies 
is  in  dispute  between  zoologists  and  botanists,  and  as  I  have 
included  the  group  in  the  zoological  classification,  agreeing 
that  its  traits  are  more  animal  than  vegetal,  I  cannot  also 
include  it  in  the  botanical  classification. 

Here,  linear  arrangement  has  disappeared:  there  is  a 
breaking  up  into  groups  and  sub-groups  and  sub-sub-groups, 
which  do  not  admit  of  being  placed  in  serial  order,  but  only 
in  divergent  and  re-divergent  order.  Were  there  space  to 
exhibit  the  way  in  which  the  Alliances  are  subdivided  into 
Orders,  and  these  into  Genera,  and  these  into  Species,  the 
same  principle  of  co-ordination  would  be  still  further  mani- 


HYLA. 


SUB- PHYLA. 


THALLOPHYTA 


CLASSES. 


I.  Schizophyta. . 

II.  Dinoflagellata 

Peridineae  . 

HI.  Bacillariales.. 


SUB-CLASSES. 


IV.  Gamophyceae  . .   I.  Chlorophycese 


ALLIANCES. 

2.  Cyanophyceas. 

Blue-green  Alg 

3.  Schlzomycetes. 


4. 
5. 

6.  Protococcoideae 

7.  Siphoneae. 

8.  Confervoideae. 

9.  Conjugates. 

10.  Charales. 

11.  Phaeophyceae. 

12.  Dictyotales. 

13.  Florideee,  Red  S< 

weeds. 


I.  Phycomycetes  I  j*' 
V.  Fungi -j    II.  Mesomycetes   j  jf; 


ARCHEGONIATJi:.... 


Bryophyta 


II.  Ptcridophyta, 

Vas.  Cryptogams 


III.  Mycomycetes   j  |°- 
Additional  group  of  Fungi,  Lichenes. 

f20.  Hepaticae,     Lh 
1          worts. 

( 21.  Musci,  Mosses. 

f22.  Filices,  Ferns. 

23.  Hydropterides, 

Rhizocarps. 

24.  Equisetales, 

Horse-tails. 

25.  Lycopodiales, 

Club-mosses. 


PHANEROGAMIA 

(Flowering  Plants.) 


I.  Cycadales,  Cycads 26. 

II.  Coniferse 27. 

III.  Gnetales 


I.  Monocotyledons.. 


II.  Dicotyledons 


28. 

29.  Liliiflora?. 

30.  Scitamineae. 

32!  Fluviales.  ' 

33.  Spadiciflorae. 

34.  GlumifloraB. 
(35.  Centrospermae. 

36.  Protiales. 

I  37.  Daphnales. 

I  38.  Santalales. 

I  39.  Rafflesiales. 

I.  Monochlamydae    40.  Asarales. 

41.  Euphorbiales. 


II.  Monopetalae. . 


43.  Viridiflorae. 

44.  Amentales. 
[45.  Balanophoralei 
f46.  Caprifoliales. 

47.  Asterales. 
I  48.  Campanales. 

49.  Ericales. 

50.  Vaccinales. 

51.  Primulales. 

52.  Tubifloras. 


III.  Polypetalte. 


54.  Parietales. 

55.  Malvales. 

56.  Disciflorae. 

57.  Crateranthse. 

58.  Myrtales. 

59.  Melastomales. 

60.  Lythrales. 

61.  Hygrobiae. 

62.  Passiflorae. 

63.  Pepones. 

64.  Cactales. 

65.  Ficoidales. 

66.  Umbellales. 

379 


380  THE  INDUCTIONS  OP  BIOLOGY. 

fested.  On  studying  the  definitions  of  these  primary,  sec- 
ondary, and  tertiary  classes,  it  will  be  found  that  the  largest 
are  marked  off  from  one  another  by  some  attribute  which  con- 
notes sundry  other  attributes ;  that  each  of  the  smaller  classes 
comprehended  in  one  of  these  largest  classes,  is  marked  off 
in  a  similar  way  from  the  other  smaller  classes  bound  up  with 
it;  and  that  so,  each  successively  smaller  class  has  an  in- 
creased number  of  co-existing  attributes. 

§  100.  Zoological  classification  has  had  a  parallel  history. 
The  first  attempt  which  we  need  notice,  to  arrange  animals 
in  such  a  way  as  to  display  their  affinities,  is  that  of  Lin- 
nasus.  He  grouped  them  thus :  * — 

CL.  1.  MAMMALIA.  Ord.  Primates,  Bruta,  Ferae,  Glires,  Pecora, 
Belluse,  Cete. 

CL.  2.  AVES.  Ord.  Accipitres,  Picas,  Anseres,  Grallse,  Gallinae, 
Passeres. 

CL.  3.  AMPHIBIA.    Ord.  Reptiles,  Serpentes,  Nantes. 

CL.  4.  PISCES.   Ord.  Apodes,  Jugulares,  Thoracici,  Abdominales. 

CL.  5.  INSECTA.  Ord.  Coleoptera,  Hemiptera,  Lepidoptera,  Neu- 
roptera,  Diptera,  Aptera. 

CL.  6.  VERMES.  Ord.  Intestina,  Mollusca,  Testacea,  Lithophyta, 
Zoophyta. 

This  arrangement  of  classes  is  obviously  based  on  ap- 
parent gradations  of  rank;  and  the  placing  of  the  orders 
similarly  betrays  an  endeavour  to  make  successions,  begin- 
ning with  the  most  superior  forms  and  ending  with  the 
most  inferior  forms.  While  the  general  and  vague  idea  of 
perfection  determines  the  leading  character  of  the  classifi- 
cation, its  detailed  groupings  are  determined  by  the  most 
conspicuous  external  attributes.  Not  only  Linnaeus  but 
his  opponents,  who  proposed  other  systems,  were  "under 
the  impression  that  animals  were  to  be  arranged  together 
into  classes,  orders,  genera,  and  species,  according  to  their 

*  This  classification,  and  the  three  which  follow  it,  I  quote  (abridging 
some  of  them)  from  Prof.  Agassiz's  "  Essa7  on  Classification." 


CLASSIFICATION.  381 

more  or  less  close  external  resemblance."  This  conception 
survived  until  the  time  of  Cuvier.  "  Naturalists,"  says  Agas- 
siz,  "  were  bent  upon  establishing  one  continual  uniform 
series  to  embrace  all  animals,  between  the  links  of  which  it 
was  supposed  there  were  no  unequal  intervals.  The  watch- 
word of  their  school  was:  Natura  non  facit  saltum.  They 
called  their  system  la  chaine  des  etres." 

The  classification  of  Cuvier,  based  on  internal  organization 
instead  of  external  appearance,  was  a  great  advance.  He 
asserted  that  there  are  four  principal  forms,  or  four  general 
plans,  on  which  animals  are  constructed;  and,  in  pursuance 
of  this  assertion,  he  drew  out  the  following  scheme. 

First  Branch.     ANIMALIA  VERTEBRATA. 
Cl.  1.  Mammalia. 
Cl.  2.  Birds. 
Cl.  3.  Reptilia. 
Cl.  4.  Fishes. 

Second  Branch.     ANIMALIA  MOLLUSCA. 
Cl.  1.  Cephalapoda. 
Cl.  2.  Pteropoda. 
Cl.  3.  Gasteropoda. 
Cl.  4.  Acephala. 
Cl.  5.  Brachiopoda. 
Cl.  6.  Cirrhopoda. 

Third  Branch.     ANIMALIA  ARTICULATA. 
Cl.  1.  Annelides. 
Cl.  2.  Crustacea. 
Cl.  3.  Arachnides. 
Cl.  4.  Insects. 

Fourth  Branch.     ANIMALIA  RADIATA. 
Cl.  1.  Echinoderms. 
Cl.  2.  Intestinal  Worms. 
Cl.  3.  Acalephse. 
Cl.  4.  Polypi. 
Cl.  5.  Infusoria. 


382 


THE  INDUCTIONS  OF  BIOLOGY. 


But  though  Cuvier  emancipated  himself  from  the  concep- 
tion of  a  serial  progression  throughout  the  Animal  Kingdom, 
sundry  of  his  contemporaries  and  successors  remained  fet- 
tered by  the  old  error.  Less  regardful  of  the  differently- 
combined  sets  of  attributes  distinguishing  the  different  sub- 
kingdoms,  and  swayed  by  the  belief  in  a  progressive  develop- 
ment which  was  erroneously  supposed  to  imply  a  linear  ar- 
rangement of  animals,  they  persisted  in  thrusting  organic 
forms  into  a  quite  unnatural  order.  The  following  classifi- 
cation of  Lamarck  illustrates  this. 

INVERTEBRATA. 


I.  APATHETIC  ANIMALS. 

Cl.    1.  Infusoria. 
Cl.    2.  Polypi. 
Cl.    3.  Radiaria. 
Cl.    4.  Tunicata. 
Cl.    5.  Vermes. 

II.  SENSITIVE  ANIMALS. 

Cl.    6.  Insects. 

Cl.    7.  Arachnids. 

Cl.    8.  Crustacea. 

Cl.    9.  Annelids. 

Cl.  10.  Cirripeds. 

Cl.  11.  Conchifera. 

Cl.  12.  Mollusks. 


Do  not  feel,  and  move  only  by  their 
excited  irritability.  No  brain,  no 
elongated  medullary  mass ;  no  senses ; 
forms  varied ;  rarely  articulations.! 


Feel,  but  obtain  from  their  sensa- 
tions only  perceptions  of  objects,  a 
sort  of  simple  ideas,  which  [they  are 
unable  to  combine  to  obtain  complex 
ones.  No  vertebral  column ;  a  brain 
and  mostly  an  elongated  medullary 
mass ;  some  distinct  senses ;  muscles 
attached  under  the  skin;  form  sym- 
metrical, the  parts  being  in  pairs. 


VERTEBRATA. 


III.  INTELLIGENT  ANIMALS. 
Cl.  13.  Fishes. 
Cl.  14.  Reptiles. 
Cl.  15.  Birds. 
Cl.  16.  Mammalia. 


Feel  ;  acquire  preservable  ideas  ; 
perform  with  them  operations  by  which 
they  obtain  others  ;  are  intelligent  in 
different  degrees.  A  vertebral  column  ; 
a  brain  and  a  spinal  marrow  ;  distinct 
senses  ;  the  muscles  attached  to  the 
internal  skeleton;  form  symmetrical, 
the  parts  being  in  pairs. 


Passing  over  sundry  classifications  in  which  the  serial 
arrangement  dictated  by  the  notion  of  ascending  complexity, 
is  variously  modified  by  the  recognition  of  conspicuous 
anatomical  facts,  we  come  to  classifications  which  recognize 


CLASSIFICATION.  383 

another  order  of  facts — those  of  development.     The  embryo- 
logical  inquiries  of  Von  Baer  led  him  to  arrange  animals  as 
follows : — 
I.  Peripherie  Type.     (RADIATA.)     Evolutio  radiata.    The 

development  proceeds  from  a  centre,  producing  identical  parts  in  a 
radiating  order. 

II.  Massive  Type.      (  MOLLUSC  A.)     Evolutio  contorta.    The 

development  produces  identical  parts  curved  around  a  conical  or  other 
space. 

III.  Longitudinal  Type.     (AKTICULATA.)     Evolutio  gemina. 

The  development  produces  identical  parts  arising  on  both  sides  of  an 
axis,  and  closing  up  along  a  line  opposite  the  axis. 

IV.  Doubly  Symmetrical  Type.     (VEETEBRATA.)    Evolutio 

bigemina.  The  development  produces  identical  parts  arising  on  both 
sides  of  an  axis,  growing  upwards  and  downwards,  and  shutting  up 
along  two  lines,  so  that  the  inner  layer  of  the  gerrn  is  inclosed  below, 
and  the  upper  layer  above.  The  embryos  of  these  animals  have  a  dorsal 
cord,  dorsal  plates,  and  ventral  plates,  a  nervous  tube  and  branchial 
fissures. 

Recognizing  these  fundamental  differences  in  the  modes  of 
development,  as  answering  to  fundamental  divisions  in  the 
animal  kingdom,  Von  Baer  shows  (among  the  Vertebrata  at 
least)  how  the  minor  differences  which  arise  at  successively 
later  embryonic  stages,  correspond  with  the  minor  divisions. 

Like  the  modern  classification  of  plants,  the  modern  classi- 
fication of  animals  shows  us  the  assumed  linear  order  com- 
pletely broken  up.  In  his  lectures  at  the  Royal  Institution,  in 
1857,  Prof.  Huxley  expressed  the  relations  existing  among 
the  several  great  groups  of  the  animal  kingdom,  by  placing 
them  at  the  ends  of  four  or  five  radii,  diverging  from 
a  centre.  The  diagram  I  cannot  obtain;  but  in  the  pub- 
lished reports  of  his  lectures  at  the  School  of  Mines 
the  groups  were  arranged  as  on  the  following  page. 
What  remnant  there  may  seem  to  be  of  linear  succession 
in  some  of  the  sub-groups  contained  in  it,  is  merely  an  acci- 
dent of  typographical  convenience.  Each  of  them  is  to  be 
regarded  simply  as  a  cluster.  And  if  Prof.  Huxley  had  fur- 
ther developed  the  arrangement,  by  dispersing  the  sub-groups 


384  THE   INDUCTIONS  OF   BIOLOGY. 

and  sub-sub-groups  on  the  same  principle,  there  would  result 
an  arrangement  perhaps  not  much  unlike  that  shown  on 
the  page  succeeding  this. 

VERTEBRATA 

(Abranchiata,) 
Mammalia 

Aves 

Reptilia 

(Branchiata) 

Amphibia 

Pisces. 

MOLLUSCA  ANNULOSA 

Cephalopoda      Heteropoda     \  Articuldta. 

Gasteropoda-  >         Insecta  Arachuida 

direcia         )          Myriapoda          Crustacea 
\  Pulmonata          Gasteropoda- 
\  Pteropoda  monoecia  Annuloida. 

Lamellibranchiata  Annellata  Scoleidse 

Echinodermata     Trematoda 
Rotifera  Tceniadse 

Turbellaria 
Nematoidea 
C(ELENTERATA 

Hydrozoa  Actinozoa. 

PROTOZOA 

Infusoria  Spongiada?  Gregarinidse 

Noctiliicidce  Foraminifera  Thallassicollida 

In  the  woodcut,  the  dots  represent  orders,  the  names  of 
which  it  is  impracticable  to  insert.  If  it  be  supposed  that 
when  magnified,  each  of  these  dots  resolves  itself  into  a 
cluster  of  clusters,  representing  genera  and  species,  an  ap- 
proximate idea  will  be  formed  of  the  relations  among  the 
successively-subordinate  groups  constituting  the  animal  king- 
dom. Besides  the  subordination  of  groups  and  their  general 
distribution,  some  other  facts  are  indicated.  By  the  distances 
of  the  great  divisions  from  the  general  centre,  are  rudely 


CLASSIFICATION.  3S5 

symbolized  their  respective  degrees  of  divergence  from  the 
form  of  simple,  undifferentiated  organic  matter;  which  we 
may  regard  as  their  common  source.  Within  each  group, 
the  remoteness  from  the  local  centre  represents,  in  a  rough 


V      '  •  ••*  Art* 

'  .:;   Refitilia. 

VE    RTEIB'RATA 


\ 

\  /  .*,*  *Crti3tacta 

\  ArticUlata. 


\ 


/  iMyria/ioda 
I 

A  N  N  y  L  9  S.  A 


Ptcre/icita          ,  ir/maufltta.  -^ 

•-.'diwia  \  / 

Gastercfada.  'Palme  not  a  \  I 

mcnaci  a.     •  • 

M  O  L  L  U   S  C  A 

lamttiibra. 


\Bractiu>/i.cda 

M  ollu  s  c  6Tda  "  "  " 

«  0  a  /PROTOZOA 

*  S  Infusoria 


CCEL  E  N  TE1RATA 


way,  the  degree  of  departure  from  the  general  plan  of  the 
group.  And  the  distribution  of  the  sub-groups  within  each 
group,  is  in  most  cases  such  that  those  which  come  nearest 
to  neighbouring  groups,  are  those  which  show  the  nearest 


386  THE  INDUCTIONS  OP  BIOLOGY. 

resemblances  to  them — in  their  analogies  though  not  in  their 
homologies.  Xo  such  scheme,  however,  can  give  a  correct  con- 
ception. Even  supposing  the  above  diagram  expressed  the 
relations  of  animals  to  one  another  as  truly  as  they  can  be 
expressed  on  a  plane  surface  (which  of  course  it  does  not),  it 
would  still  be  inadequate.  Such  relations  cannot  be  repre- 
sented in  space  of  two  dimensions,  but  only  in  space  of  three 
dimensions. 

§  lOOa.  Two  motives  have  prompted  me  to  include  in  its 
original  form  the  foregoing  sketch:  the  one  being  that  in 
conformity  with  the  course  previously  pursued,  of  giving  the 
successive  forms  of  classifications,  it  seems  desirable  to  give 
this  form  which  was  approved  thirty-odd  years  ago ;  and  the 
other  being  that  the  explanatory  comments  remain  now  as 
applicable  as  they  were  then.  Replacement  of  the  diagram 
by  one  expressing  the  relations  of  classes  as  they  are  now 
conceived,  is  by  no  means  an  easy  task;  for  the  conceptions 
formed  of  them  are  unsettled.  Concerning  the  present  atti- 
tude of  zoologists,  Prof.  MacBride  writes : — 

"They  all  recognize  a  certain  number  of  phyla.  Each  phylum 
includes  a  group  of  animals  about  whose  relation  to  each  other  no  one 
entertains  a  doubt.  Each  zoologist,  however,  has  his  own  idea  as  to 
the  relationship  which  the  various  phyla  bear  to  each  other. 

"  The  phyla  recognized  at  present  are : — 

"  (1)  Protozoa. 

"  (2)  Porifera  (Sponges). 

"(3)  Co3lenterata. 

"  (4)  Echinodermata. 

c  Cestodes. 

"  (5)  Platyhelminthes  j  Trematodes. 
(  Turbellaria. 

"(6)  Nemertea. 

«:  (7)  Nematoda. 

"  (8)  Acanthocephala  (Echinorhyncus). 

"  (9)  Chsetognatha  (Sagitta). 

"  (10)  Rotifera. 

"(11)  Annelida  (Includes  Leeches  and  Gephyrea,  Chaetifera). 

"  (12)  Gephyrea,  Achata. 


CLASSIFICATION.  387 

f  Tracheata  (Peripatus,  Myriapods,  Insects). 

(13)  Arthropods  J  Arachnids- 
]  Crustacea. 


Pycnogonida. 
•'(U)Mollusca. 

"  (15)  Polyzoa  (Including  Phoronis). 

«  (16)  Brachiopoda. 

"  (17)  Chordata  (Includes  Balanoglossus  and   Tunicates.      Some 

continental  zoologists  do  not  admit  Balanoglossus)." 
[This  last  phylum  of  course  includes  the  Vertebrate.] 

Though  under  present  conditions,  as  above  implied,  it 
would  be  absurd  to  attempt  a  definite  scheme  of  relation- 
ships, yet  it  has  seemed  to  me  that  the  adumbration  of  a 
scheme,  presenting  in  a  vague  way  such  relationships  as  are 
generally  agreed  upon  and  leaving  others  indeterminate,  may 
be  ventured;  and  that  a  general  impression  hence  resulting 
may  be  useful.  On  the  adjacent  page  I  have  tried  to  make 
a  tentative  arrangement  of  this  kind. 

At  the  bottom  of  the  table  I  have  placed  together,  under 
the  name  "  Compound  Protozoa"  those  kinds  of  aggregated 
Protozoa  which  show  no  differentiations  among  the  members 
of  groups,  and  are  thus  distinguished  from  Metazoa;  and  I 
have  further  marked  the  distinction  by  their  position,  which 
implies  that  from  them  no  evolution  of  higher  types  has  taken 
place.  Eespecting  the  naming  of  the  sub-kingdoms,  phyla, 
classes,  orders,  &c.,  I  have  not  maintained  entire  consistency. 
The  relative  values  of  groups  cannot  be  typographically  ex- 
pressed in  a  small  space  with  a  limited  variety  of  letters. 
The  sizes  of  the  letters  mark  the  classificatory  ranks,  and 
by  the  thickness  I  have  rudely  indicated  their  zoological  im- 
portance. In  fixing  the  order  of  subordination  of  groups 
I  have  been  aided  by  the  table  of  contents  prefixed  to  Mr. 
Adam  Sedgwick's  Student's  Text  Book  of  Zoology  and  have 
also  made  use  of  Prof.  Eay  Lankester's  classifications  of 
several  sub-kingdoms. 

Let  me  again  emphasize  the  fact  that  the  relationships  of 
these  diverging  and  re-diverging  groups  cannot  be  expressed 


CLASSIFICATION.  389 

on  a  flat  surface.  If  we  imagine  a  laurel-bush  to  be  squashed 
flat  by  a  horizontal  plane  descending  upon  it,  we  shall  see 
that  sundry  of  the  upper  branches  and  twigs  which  were 
previously  close  together  will  become  remote,  and  that  the 
relative  positions  of  parts  can  remain  partially  true  only 
with  the  minor  branches.  The  reader  must  therefore  expect 
to  find  some  of  the  zoological  divisions  which  in  the  order  of 
nature  are  near  one  another,  shown  in  the  table  as  quite 
distant. 

§  101.  While  the  classifications  of  botanists  and  zoologists 
have  become  more  and  more  natural  in  their  arrangements, 
there  has  grown  up  a  certain  artificiality  in  their  abstract 
nomenclature.  When  aggregating  the  smallest  groups  into 
larger  groups  and  these  into  groups  still  larger,  they  have 
adopted  certain  general  terms  expressive  of  the  successively 
more  comprehensive  divisions ;  and  the  habitual  use  of  these 
terms,  needful  for  purposes  of  convenience,  has  led  to  the 
tacit  assumption  that  they  answer  to  actualities  in  Nature. 
It  has  been  taken  for  granted  that  species,  genera,  orders, 
and  classes,  are  assemblages  of  definite  values — that  every 
genus  is  the  equivalent  of  every  other  genus  in  respect  of  its 
degree  of  distinctness;  and  that  orders  are  separated  by 
lines  of  damarcation  which  are  as  broad  in  one  place  as 
another.  Though  this  conviction  is  not  a  formulated  one, 
the  disputes  continually  occurring  among  naturalists  on 
the  questions,  whether  such  and  such  organisms  are  specifi- 
cally or  generically  distinct,  and  whether  this  or  that  pecu- 
liarity is  or  is  not  of  ordinal  importance,  imply  that  the 
conviction  is  entertained  even  where  not  avowed.  Yet  that 
differences  of  opinion  like  these  arise  and  remain  unsettled, 
except  when  they  end  in  the  establishment  of  sub-species, 
sub-genera,  sub-orders,  and  sub-classes,  sufficiently  shows 
that  the  conviction  is  ill-based.  And  this  is  equally  shown 
by  the  impossibility  of  obtaining  any  definition  of  the  degree 
of  difference  which  warrants  each  further  elevation  in  the 
hierarchy  of  classes. 
26 


390  THE  INDUCTIONS  OP  BIOLOGY. 

It  is,  indeed,  a  wholly  gratuitous  assumption  that  organ- 
isms admit  of  being  placed  in  groups  of  equivalent  values; 
and  that  these  may  be  united  into  larger  groups  which  are 
also  of  equivalent  values;  and  so  on.  There  is  no  a  priori 
reason  for  expecting  this;  and  there  is  no  a  posteriori  evi- 
dence implying  it,  save  that  which  begs  the  question — that 
which  asserts  one  distinction  to  be  generic  and  another  to  be 
ordinal,  because  it  is  assumed  that  such  distinctions  must  be 
either  generic  or  ordinal.  The  endeavour  to  thrust  plants 
and  animals  into  these  definite  partitions  is  of  the  same 
nature  as  the  endeavour  to  thrust  them  into  linear  series. 
Not  that  it  does  violence  to  the  facts  in  anything  like  the 
same  degree;  but  still,  it  does  violence  to  the  facts.  Doubt- 
less the  making  of  divisions  and  sub-divisions,  is  extremely 
useful ;  or  rather,  it  is  necessary.  Doubtless,  too,  in  reducing 
the  facts  to  something  like  order  they  must  be  partially  dis- 
torted. So  long  as  the  distorted  form  is  not  mistaken  for  the 
actual  form,  no  harm  results.  But  it  is  needful  for  us  to 
remember  that  while  our  successively  subordinate  groups 
have  a  certain  general  correspondence  with  the  realities,  they 
tacitly  ascribe  to  the  realities  a  regularity  which  does  not 
exist. 

§  102.  A  general  truth  of  much  significance  is  exhibited 
in  these  classifications.  On  observing  the  natures  of  the 
attributes  which  are  common  to  the  members  of  any  group 
of  the  first,  second,  third,  or  fourth  rank,  we  see  that  groups 
of  the  widest  generality  are  based  on  characters  of  the  greatest 
importance,  physiologically  considered;  and  that  the  charac- 
ters of  the  successively-subordinate  groups,  are  characters  of 
successively-subordinate  importance.  The  structural  pecu- 
liarity in  which  all  members  of  one  sub-kingdom  differ  from 
all  members  of  another  sub-kingdom,  is  a  peculiarity  that 
affects  the  vital  actions  more  profoundly  than  does  the  struc- 
tural peculiarity  which  distinguishes  all  members  of  one 
class  from  all  members  of  another  class.  Let  us  look  at  a 
few  cases. 


CLASSIFICATION.  391 

We  saw  (§  56),  that  the  broadest  division  among  the 
functions  is  the  division  into  "  the  accumulation  of  energy 
(latent  in  food) ;  the  expenditure  of  energy  (latent  in  the 
tissues  and  certain  matters  absorbed  by  them) ;  and  the 
transfer  of  energy  (latent 'in  the  prepared  nutriment  or  blood) 
from  the  parts  which  accumulate  to  the  parts  which  expend." 
Now  in  the  lowest  animals,  united  under  the  general  name 
Protozoa,  there  is  either  no  separation  of  the  parts  performing 
these  functions  or  very  indistinct  separation:  in  the  Rhizo- 
poda,  all  parts  are  alike  accumulators  of  energy,  expenders  of 
energy  and  transferors  of  energy;  and  though  in  the  higher 
members  of  the  group,  the  Infusoria,  there  are  some  speciali- 
zations corresponding  to  these  functions,  yet  there  are  no 
distinct  tissues  appropriated  to  them.  Similarly  when  we 
pass  from  simple  types  to  compound  types — from  Protozoa  to 
Metazoa.  The  animals  known  as  Ccelenterata  are  charac- 
terized in  common  by  the  possession  of  a  part  which  accumu- 
lates energy  more  or  less  marked  off  from  the  part  which 
does  not  accumulate  energy,  but  only  expends  it;  and  the 
Hydrozoa  and  Actinozoa,  which  are  sub-divisions  of  the 
Ccelenterata,  are  contrasted  in  this,  that  in  the  second  these 
parts  are  much  more  differentiated  from  one  another,  as  well 
as  more  complicated.  Besides  a  completer  differentiation  of 
the  organs  respectively  devoted  to  the  accumulation  of 
energy  and  the  expenditure  of  energy,  animals  next  above 
the  Codenterata  possess  rude  appliances  for  the  transfer  of 
energy:  the  peri-visceral  sac,  or  closed  cavity  between  the 
intestine  and  the  walls  of  the  body,  serves  as  a  reservoir  of 
absorbed  nutriment,  from  which  the  surrounding  tissues  take 
up  the  materials  they  need.  And  then  out  of  this  sac 
originates  a  more  efficient  appliance  for  the  transfer  of  ener- 
gy: the  more  highly-organized  animals,  belonging  to 
whichever  sub-kingdom,  all  of  them  possess  definitely-con- 
structed channels  for  distributing  the  matters  containing 
energy.  In  all  of  them,  too,  the  function  of  expenditure  is 
divided  between  a  directive  apparatus  and  an  executive 


392  THE  INDUCTIONS  OF  BIOLOGY. 

apparatus — a  nervous  system  and  a  muscular  system.  But 
these  higher  sub-kingdoms  are  clearly  separated  from  one 
another  by  differences  in  the  relative  positions  of  their  com- 
ponent sets  of  organs.  The  habitual  attitudes  of  annulose 
and  molluscous  creatures,  is  such  that  the  neural  centres  are 
below  the  alimentary  canal  and  the  haemal  centres  above. 
And  while  by  these  traits  the  annulose  and  molluscous  types 
are  separated  from  the  vertebrate,  they  are  separated  from 
each  other  by  this,  that  in  the  one  the  body  is  "  composed  of 
successive  segments,  usually  provided  with  limbs,"  but  in  the 
other,  the  body  is  not  segmented,  "  and  no  true  articulated 
limbs  are  ever  developed." 

The  sub-kingdoms  being  thus  distinguished  from  one  an- 
other, by  the  presence  or  absence  of  specialized  parts  devoted 
to  fundamental  functions,  or  else  by  differences  in  the  distri- 
butions of  such  parts,  we  find,  on  descending  to  the  classes, 
that  these  are  distinguished  from  one  another,  either  by 
modifications  in  the  structures  of  fundamental  parts,  or  by 
the  presence  or  absence  of  subsidiary  parts,  or  by  both. 
Fishes  and  Amphibia  are  unlike  higher  vertebrates  in  possess- 
ing branchiae,  either  throughout  life  or  early  in  life.  And 
every  higher  vertebrate,  besides  having  lungs,  is  characterized 
by  having,  during  development,  an  amnion  and  an  allantois. 
Mammals,  again,  are  marked  off  from  Birds  and  Reptiles  by 
the  presence  of  mammae,  as  well  as  by  the  form  of  the 
occipital  condyles.  Among  Mammals,  the  next  division  is 
based  on  the  presence  or  absence  of  a  placenta.  And  divisions 
of  the  Placentalia  are  mainly  determined  by  the  characters 
of  the  organs  of  external  action. 

Thus,  without  multiplying  illustrations  and  without  de- 
scending to  genera  and  species,  we  see  that,  speaking  gener- 
ally, the  successively  smaller  groups  are  distinguished  from 
one  another  by  traits  of  successively  less  importance,  physic- 
logically  considered.  The  attributes  possessed  in  common 
by  the  largest  assemblages  of  organisms,  are  few  in  number 
but  all-essential  in  kind.  Each  secondary  assemblage,  in- 


CLASSIFICATION.  393 

eluded  in  one  of  the  primary  assemblages,  is  characterized  by 
further  common  attributes  that  influence  the  functions  less 
profoundly.  And  so  on  with  each  lower  grade. 

§  103.  What  interpretation  is  to  be  put  on  these  truths  of 
classification?  We  find  that  organic  forms  admit  of  an 
arrangement  everywhere  indicating  the  fact,  that  along  with 
certain  attributes,  certain  other  attributes,  which  are  not 
directly  connected  with  them,  always  exist.  How  are  we 
to  account  for  this  fact?  And  how  are  we  to  account  for 
the  fact  that  the  attributes  possessed  in  common  by  the 
largest  assemblages  of  forms,  are  the  most  vitally-important 
attributes  ? 

No  one  can  believe  that  combinations  of  this  kind  have 
arisen  fortuitously.  Even  supposing  fortuitous  combina- 
tions of  attributes  might  produce  organisms  that  would  work, 
we  should  still  be  without  a  clue  to  this  special  mode  of 
combination.  The  chances  would  be  infinity  to  one  against 
organisms  which  possessed  in  common  certain  fundamental 
attributes,  having  also  in  common  numerous  non-essential 
attributes. 

Nor,  again,  can  any  one  allege  that  such  combinations  are 
necessary,  in  the  sense  that  all  other  combinations  are  im- 
practicable. There  is  not,  in  the  nature  of  things,  a  reason 
why  creatures  covered  with  feathers  should  always  have 
beaks:  jaws  carrying  teeth  would,  in  many  cases,  have 
served  them  equally  well  or  better.  The  most  general 
characteristic  of  an  entire  sub-kingdom,  equal  in  extent 
to  the  V ' ertebrata,  might  have  been  the  possession  of  nicti- 
tating membranes;  while  the  internal  organizations  through- 
out this  sub-kingdom  might  have  been  on  many  different 
plans. 

If,  as  an  alternative,  this  peculiar  subordination  of  traits 
which  organic  forms  display  be  ascribed  to  design,  other 
difficulties  suggest  themselves.  To  suppose  that  a  certain 
plan  of  organization  was  fixed  on  by  a  Creator  for  each  vast 


394  THE  INDUCTIONS  OF  BIOLOGY. 

and  varied  group,  the  members  of  which  were  to  have  many 
different  modes  of  life,  and  that  he  bound  himself  to  adhere 
rigidly  to  this  plan,  even  in  the  most  aberrant  forms  of  the 
group  where  some  other  plan  would  have  been  more  appro- 
priate, is  to  ascribe  a  very  strange  motive.  When  we  dis- 
cover that  the  possession  of  seven  cervical  vertebrae  is  a  gen- 
eral characteristic  of  mammals,  whether  the  neck  be  im- 
mensely long  as  in  the  giraffe,  or  quite  rudimentary  as  in 
the  whale,  shall  we  say  that  though,  for  the  whale's  neck, 
one  vertebra  would  have  been  equally  good,  and  though,  for 
the  giraffe's  neck,  a  dozen  would  probably  have  been  better 
than  seven,  yet  seven  was  the  number  adhered  to  in  both 
cases,  because  seven  was  fixed  upon  for  the  mammalian  type? 
And  then,  when  it  turns  out  that  this  possession  of  seven 
cervical  vertebra?  is  not  an  absolutely-universal  characteristic 
of  mammals  (there  is  one  which  has  eight),  shall  we  conclude 
that  while,  in  a  host  of  cases,  there  was  a  needless  adherence 
to  a  plan  for  the  sake  of  consistency,  there  was  yet,  in  some 
cases,  an  inconsistent  abandonment  of  the  plan?  I  think 
we  may  properly  refuse  to  draw  any  such  conclusion. 

What,  then,  is  the  meaning  of  these  peculiar  relations  of 
organic  forms?  The  answer  to  this  question  must  be  post- 
poned. Having  here  contemplated  the  problem  as  presented 
in  these  wide  inductions  which  naturalists  have  reached ;  and 
having  seen  what  proposed  solutions  of  it  are  inadmissible; 
we  shall  see,  in  the  next  division  of  this  work,  what  is  the 
only  possible  solution. 


CHAPTER  XII. 

DISTRIBUTION. 

§  104.  THERE  is  a  distribution  of  organisms  in  Space,  and 
there  is  a  distribution  of  organisms  in  Time.  Looking  first 
at  their  distribution  in  Space,  we  observe  in  it  two  different 
classes  of  facts.  On  the  one  hand,  the  plants  and  animals  of 
each  species  have  their  habitats  limited  by  external  condi- 
tions :  they  are  necessarily  restricted  to  spaces  in  which  their 
vital  actions  can  be  performed.  On  the  other  hand,  the 
existence  of  certain  conditions  does  not  determine  the  pres- 
ence of  organisms  that  are  fit  for  them.  There  are  many 
spaces  perfectly  adapted  for  life  of  a  high  order  in  which 
only  life  of  a  much  lower  order  is  found. 

While,  in  the  inevitable  restriction  of  organisms  to  environ- 
ments with  which  their  natures  correspond  we  find  a  negative 
cause  of  distribution,  there  remains  to  be  found  that  positive 
cause  whence  results  the  presence  of  organisms  in  some  places 
appropriate  to  them  and  their  absence  from  other  places 
equally  appropriate  or  more  appropriate.  Let  us  consider  the 
phenomena  as  thus  classed. 

§  105.  Facts  which  illustrate  the  limiting  influence  of  sur- 
rounding conditions  are  abundant,  and  familiar  to  all  readers. 
It  will  be  needful,  however,  here  to  cite  a  few  typical  ones 
of  each  order. 

The  confinement  of  different  kinds  of  plants  and  different 

895 


396  THE  INDUCTIONS  OF  BIOLOGY. 

kinds  of  animals,  to  the  media  for  which  they  are  severally 
adapted,  is  the  broadest  fact  of  distribution.  We  have  ex- 
tensive groups  of  plants  that  are  respectively  sub-aerial  and 
sub-aqueous;  and  of  the  sub-aqueous  some  are  exclusively 
marine,  while  others  exist  ony  in  rivers  and  lakes.  Among 
animals  we  similarly  find  some  classes  confined  to  the  air 
and  others  to  the  water;  and  of  the  water-breathers  some 
are  restricted  to  salt  water  and  others  to  fresh  water.  Less 
conspicuous  is  the  fact  that  within  each  of  these  contrasted 
media  there  are  further  widespread  limitations.  In  the  sea, 
certain  organisms  exist  only  between  certain  depths,  and 
others  only  between  other  depths — the  limpet  and  the  mussel 
within  the  littoral  zone,  and  numerous  kinds  at  the  bottom 
of  the  ocean;  and  on  the  land,  there  are  Floras  and  Faunas 
peculiar  to  low  regions  and  others  peculiar  to  high  regions. 
Next  we  have  the  familiar  geographical  limitations  made  by 
climate.  There  are  temperatures  which  restrict  each  kind  of 
organism  between  certain  isothermal  lines,  and  hygrometric 
states  which  prevent  the  spread  of  each  kind  of  organism 
beyond  areas  having  a  certain  humidity  or  a  certain  dryness. 
Besides  such  general  limitations  we  find  much  more  special 
limitations.  Some  minute  vegetal  forms  occur  only  in  snow. 
Hot  springs  have  their  peculiar  Infusoria.  The  habitats  of 
certain  Fungi  are  mines  or  other  dark  places.  And  there  are 
creatures  unknown  beyond  the  water  contained  in  particular 
caves.  After  these  limits  to  distribution  imposed  by 

physical  conditions,  come  limits  imposed  by  the  presence  or 
absence  of  other  organisms.  Obviously,  graminivorous  animals 
are  confined  within  tracts  which  produce  plants  fit  for  them 
to  feed  on.  The  great  carnivores  cannot  exist  out  of  regions 
where  there  are  creatures  large  enough  and  numerous  enough 
to  serve  for  prey.  The  needs  of  the  sloth  limit  it  to  certain 
forest-covered  spaces;  and  there  can  be  no  insectivorous  bats 
where  there  are  no  night-flying  insects.  To  these  dependences 
of  the  relatively-superior  organisms  on  the  relatively-inferior 
organisms  which  they  consume,  must  be  added  certain 


DISTRIBUTION.  397 

reciprocal  dependences  of  the  inferior  on  the  superior. 
Mr.  Darwin's  inquiries  have  shown  how  generally  the 
fertilization  of  plants  is  due  to  the  agency  of  insects,  and 
how  certain  plants,  being  fertilizable  only  by  insects  of  cer- 
tain structures,  are  limited  to  regions  inhabited  by  insects 
of  such  structures.  Conversely,  the  spread  of  organisms 
is  often  bounded  by  the  presence  of  particular  organisms 
beyond  the  bounds — either  competing  organisms  or  organisms 
directly  inimical.  A  plant  fit  for  some  territory  adjacent  to 
its  own,  fails  to  overrun  it  because  the  territory  is  pre- 
occupied by  some  plant  which  is  its  superior,  either  in  fertility 
or  power  of  resisting  destructive  agencies;  or  else  fails 
because  there  lives  in  the  territory  some  mammal  which 
browses  on  its  foliage  or  bird  which  devours  nearly  all  its 
seeds.  Similarly,  an  area  in  which  animals  of  a  particular 
species  might  thrive,  is  not  colonized  by  them  because  they 
are  not  fleet  enough  to  escape  some  beast  of  prey  inhabiting 
this  area,  or  because  the  area  is  infested  by  some  insect 
which  destroys  them,  as  the  tsetse  destroys  the  cattle  in  parts 
of  Africa.  Yet  another  more  special  series  of  limita- 

tions accompanies  parasitism.  There  are  parasitic  plants  that 
flourish  only  on  trees  of  some  few  species,  and  others  that 
have  particular  animals  for  their  habitats — as  the  fungus 
which  is  fatal  to  the  silk-worm,  or  that  which  so  strangely 
grows  out  of  a  New  Zealand  caterpillar.  Of  animal-parasites 
various  kinds  lead  lives  involving  specialities  of  distribution. 
We  have  kinds  which  use  other  creatures  for  purposes  of 
locomotion,  as  the  Chelonobia  uses  the  turtle,  and  as  a  certain 
Actinia  uses  the  shell  inhabited  by  a  hermit-crab.  We  have 
the  parasitism  in  which  one  creature  habitually  accompanies 
another  to  share  its  prey,  like  the  annelid  which  takes  up  its 
abode  in  a  hermit-crab's  shell,  and  snatches  from  the  hermit- 
crab  the  morsels  of  food  it  is  eating.  We  have  again  the 
commoner  parasitism  of  the  Epizoa — animals  which  attach 
themselves  to  the  surfaces  of  other  animals,  and  feed  on  their 
juices  or  on  their  secretions.  And  once  more,  we  have  the 


398  THE  INDUCTIONS  OF  BIOLOGY. 

equally  common  parasitism  of  the  Entozoa — creatures  which 
live  within  other  creatures.  Besides  being  restricted  to  the 
bodies  of  the  organisms  it  infests,  each  species  has  usually 
still  narrower  limits  of  distribution;  in  some  cases  the  in- 
fested organisms  furnish  fit  habitats  for  the  parasites  only 
in  certain  regions,  and  in  other  cases  only  when  in  certain 
constitutional  states.  There  are  more  indirect  modes 

in  which  the  distributions  of  organisms  affect  one  another. 
Plants  of  some  kinds  are  eaten  by  animals  only  in  the  absence 
of  kinds  that  are  preferred  to  them ;  and  hence  the  prosperity 
of  such  plants  partly  depends  on  the  presence  of  the  preferred 
plants.  Mr.  Bates  has  shown  that  some  South  American 
butterflies  thrive  in  regions  where  insectivorous  birds  would 
destroy  them,  did  they  not  closely  resemble  butterflies  of 
another  genus  which  are  disliked  by  those  birds.  And  Mr. 
Darwin  gives  cases  of  dependence  still  more  remote  and  in- 
volved. 

Such  are  the  chief  negative  causes  of  distribution — the 
inorganic  and  organic  agencies  that  set  bounds  to  the  spaces 
which  organisms  of  each  species  inhabit.  Fully  to  under- 
stand their  actions  we  must  contemplate  them  as  working 
not  separately  but  in  concert.  We  have  to  regard  the  physical 
influences,  varying  from  year  to  year,  as  now  producing  an 
extension  or  restriction  of  the  habitat  in  this  direction  and 
now  in  that,  and  as  producing  secondary  extensions  and  re- 
strictions by  their  effects  on  other  kinds  of  organisms.  We 
have  to  regard  the  distribution  of  each  species  as  affected 
not  only  by  causes  which  favour  multiplication  of  prey  or  of 
enemies  within  its  own  area,  but  also  by  causes  which  pro- 
duce such  results  in  neighbouring  areas.  We  have  to  conceive 
the  forces  by  which  the  limit  is  maintained,  as  including  all 
meteorologic  influences,  united  with  the  influences,  direct 
or  remote,  of  numerous  co-existing  species. 

One  general  truth,  indicated  by  sundry  of  the  above  illus- 
trations, calls  for  special  notice — the  truth  that  all  kinds  of 
organisms  intrude  on  one  another's  spheres  of  existence.  Of 


DISTRIBUTION.  399 

the  ways  in  which  they  do  this  the  commonest  is  invasion 
of  territory.  That  tendency  which  we  see  in  the  human  races, 
to  overrun  and  occupy  one  another's  lands,  as  well  as  the 
lands  inhabited  by  inferior  creatures,  is  a  tendency  exhibited 
by  all  classes  of  organisms  in  various  ways.  Among  them,  as 
among  mankind,  there  are  permanent  conquests,  temporary 
occupations,  and  occasional  raids.  Every  spring  an  inroad  is 
made  into  the  area  which  our  own  birds  occupy,  by  birds  from 
the  South ;  and  every  winter  the  fieldfares  of  the  North  come 
to  share  the  hips  and  haws  of  our  hedges,  and  thus  entail  on 
our  native  birds  some  mortality.  Besides  these  regularly- 
recurring  incursions  there  are  irregular  ones;  as  of  locusts 
into  countries  not  usually  visited  by  them,  or  of  certain 
rodents  which  from  time  to  time  swarm  into  areas  adjacent 
to  their  own.  Every  now  and  then  an  incursion  ends  in 
permanent  settlement — perhaps  in  conquest  over  indigenous 
species.  Within  these  few  years  an  American  water-weed 
has  taken  possession  of  our  ponds  and  rivers,  and  to  some 
extent  supplanted  native  water-weeds.  Of  animals  may  be 
named  a  small  kind  of  red  ant,  having  habits  allied  to  those 
of  tropical  ants,  which  has  of  late  overrun  many  houses  in 
London.  The  rat,  which  must  have  taken  to  infesting  ships 
within  these  few  centuries,  furnishes  a  good  illustration  of 
the  readiness  of  animals  to  occupy  new  places  that  are 
available.  And  the  way  in  which  vessels  visiting  India  are 
cleared  of  the  European  cockroach  by  the  kindred  Blatta 
orientalis,  shows  us  how  these  successful  invasions  last  only 
until  there  come  more  powerful  invaders.  Animals 

encroach  on  one  another's  spheres  of  existence  in  further 
ways  than  by  trespassing  on  one  another's  areas :  they  adopt 
one  another's  modes  of  life.  There  are  cases  in  which  this 
usurpation  of  habits  is  slight  and  temporary;  and  there  are 
cases  where  it  is  marked  and  permanent.  Grey  crows  often 
join  gulls  in  picking  up  food  between  tide-marks ;  and  gulls 
may  occasionally  be  seen  many  miles  inland,  feeding  in 
ploughed  fields  and  on  moors.  Mr.  Darwin  has  watched  a 


400  THE  INDUCTIONS  OF  BIOLOGY. 

fly-catcher  catching  fish.  He  says  that  the  greater  titmouse 
sometimes  adopts  the  practices  of  the  shrike,  and  sometimes 
of  the  nuthatch,  and  that  some  South  American  woodpeckers 
are  frugivorous  while  others  chase  insects  on  the  wing.  Of 
habitual  intrusions  on  the  occupations  of  other  creatures,  one 
case  is  furnished  by  the  sea-eagle,  which,  besides  hunting  the 
surface  of  the  land  for  prey,  like  the  rest  of  the  hawk-tribe, 
often  swoops  down  upon  fish.  And  Mr.  Darwin  names  a 
species  of  petrel  that  has  taken  to  diving,  and  has  a  consider- 
ably modified  organization.  The  last  cases  introduce 
a  still  more  remarkable  class  of  facts  of  kindred  meaning. 
This  intrusion  of  organisms  on  one  another's  modes  of  life 
goes  to  the  extent  of  intruding  on  one  another's  media.  The 
great  mass  of  flowering  plants  are  terrestrial,  and  (aside  from 
other  needs)  are  required  to  be  so  by  their  process  of  fructifi- 
cation. But  there  are  some  which  live  in  the  water,  and 
protrude  their  flowers  above  the  surface.  Nay,  there  is  a  still 
more  striking  instance.  At  the  sea-side  may  be  found  an  alga 
a  hundred  yards  inland,  and  a  phamogam  rooted  in  salt  water. 
Among  animals  these  interchanges  of  media  are  numerous. 
Nearly  all  coleopterous  insects  are  terrestrial;  but  the  water- 
beetle,  which  like  the  rest  of  its  order  is  an  air-breather,  has 
aquatic  habits.  Water  appears  to  be  an  extremely  unfit 
medium  for  a  fly;  and  yet  Mr.  [now  Sir  John]  Lubbock  has 
discovered  more  than  one  species  of  fly  living  beneath  the 
surface  of  the  water  and  coming  up  occasionally  for  air. 
Birds,  as  a  class,  are  specially  fitted  for  an  aerial  existence; 
but  certain  tribes  of  them  have  taken  to  an  aquatic  existence 
• — swimming  on  the  surface  of  the  water  and  making  continual 
incursions  beneath  it,  and  some  kinds  have  wholly  lost  the 
power  of  flight.  Among  mammals,  too,  which  have  limbs  and 
lungs  implying  an  organization  for  terrestrial  life,  may  be 
named  kinds  living  more  or  less  in  the  water  and  are  more 
or  less  adapted  to  it.  We  have  water-rats  and  otters  which 
unite  the  two  kinds  of  life,  and  show  but  little  modification ; 
hippopotami  passing  the  greater  part  of  their  time  in  the 


DISTRIBUTION.  401 

water,  and  somewhat  more  fitted  to  it;  seals  living  almost 
exclusively  in  the  sea,  and  having  the  mammalian  form 
greatly  obscured;  whales  wholly  confined  to  the  sea,  and 
having  so  little  the  aspect  of  mammals  as  to  be  mistaken  for 
fish.  Conversely,  sundry  inhabitants  of  the  water  make  ex- 
cursions on  the  land.  Eels  migrate  at  night  from  one  pool 
to  another.  There  are  fish  with  specially-modified  gills  and 
fin-rays  serving  as  stilts,  which,  when  the  rivers  they  inhabit 
are  partially  dried-up,  travel  in  search  of  better  quarters. 
And  while  some  kinds  of  crabs  do  not  make  land-excursions 
beyond  high-water  mark,  other  kinds  pursue  lives  almost 
wholly  terrestrial. 

Guided  by  these  two  classes  of  facts,  we  must  regard  the 
bounds  to  each  species'  sphere  of  existence  as  determined 
by  the  balancing  of  two  antagonist  sets  of  forces.  The  tend- 
ency which  every  species  has  to  intrude  on  other  areas,  other 
modes  of  life,  and  other  media,  is  restrained  by  the  direct 
and  indirect  resistance  of  conditions,  organic  and  inorganic. 
And  these  expansive  and  repressive  energies,  varying  con- 
tinually in  their  respective  intensities,  rhythmically  equili- 
brate each  other — maintain  a  limit  that  perpetually  oscillates 
from  side  to  side  of  a  certain  mean. 

§  106.  As  implied  at  the  outset,  the  character  of  a  region, 
when  unfavourable  to  any  species,  sufficiently  accounts  for  the 
absence  of  this  species;  and  thus  its  absence  is  not  incon- 
sistent with  the  hypothesis  that  each  species  was  originally 
placed  in  the  regions  most  favourable  to  it.  But  the  absence 
of  a  species  from  regions  that  are  favourable  to  it  cannot  be 
thus  accounted  for.  Were  plants  and  animals  localized  wholly 
with  reference  to  the  fitness  of  their  constitutions  to  surround- 
ing conditions,  we  might  expect  Floras  to  be  similar,  and 
Faunas  to  be  similar,  where  the  conditions  are  similar;  and 
we  might  expect  dissimilarities  among  Floras  and  among 
Faunas,  proportionate  to  the  dissimilarities  of  their  conditions. 
But  we  do  not  find  such  anticipations  verified. 


402  THE  INDUCTIONS  OF  BIOLOGY. 

Mr.  Darwin  says  that  "  in  the  Southern  hemisphere,  if  we 
compare  large  tracts  of  land  in  Australia,  South  Africa,  and 
western  South  America,  between  latitudes  25°  and  35°,  we 
shall  find  parts  extremely  similar  in  all  their  conditions,  yet  it 
would  not  be  possible  to  point  out  three  faunas  and  floras 
more  utterly  dissimilar.  Or  again  we  may  compare  the  pro- 
ductions of  South  America  south  of  lat.  35°  with  those  north 
of  25°,  which  consequently  inhabit  a  considerably  different  cli- 
mate, and  they  will  be  found  incomparably  more  closely  related 
to  each  other,  than  they  are  to  the  productions  of  Australia 
or  Africa  under  nearly  the  same  climate."  Still  more  striking 
are  the  contrasts  which  Mr.  Darwin  points  out  between 
adjacent  areas  that  are  totally  cut  off  from  each  other.  "  Xo 
two  marine  faunas  are  more  distinct,  with  hardly  a  fish,  shell, 
or  crab  in  common,  than  those  of  the  eastern  and  western 
shores  of  South  and  Central  America ;  yet  these  great  faunas 
are  separated  only  by  the  narrow,  but  impassable,  isthmus  of 
Panama."  On  opposite  sides  of  high  mountain-chains,  also, 
there  are  marked  differences  in  the  organic  forms — differ- 
ences not  so  marked  as  where  the  barriers  are  absolutely  im- 
passable, but  much  more  marked  than  are  necessitated  by 
unlikenesses  of  physical  conditions. 

Not  less  suggestive  is  the  converse  fact  that  wide  geogra- 
phical areas  which  offer  decided  geologic  and  meteorologic 
contrasts,  are  peopled  by  nearly-allied  groups  of  organisms,  if 
there  are  no  barriers  to  migration.  "  The  naturalist  in  tra- 
velling, for  instance,  from  north  to  south  never  fails  to  be 
struck  by  the  manner  in  which  successive  groups  of  beings, 
specifically  distinct,  yet  clearly  related,  replace  each  other. 
lie  hears  from  closely  allied,  yet  distinct  kinds  of  birds,  notes 
nearly  similar,  and  sees  their  nests  similarly  constructed, 
but  not  quite  alike,  with  eggs  coloured  in  nearly  the  same 
manner.  The  plains  near  the  Straits  of  Magellan  are  inhabit- 
ed by  one  species  of  Rhea  (American  Ostrich),  and  northward 
the  plains  of  La  Plata  by  another  species  of  the  same  genus ; 
and  not  by  a  true  ostrich  or  emu,  like  those  found  in  Africa 


DISTRIBUTION.  403 

and  Australia  under  the  same  latitude.  On  these  same  plains 
of  La  Plata,  we  see  the  agouti  and  bizcacha,  animals  having 
nearly  the  same  habits  as  our  hares  and  rabbits  and  belonging 
to  the  same  order  of  Bodents,  but  they  plainly  display  an 
American  type  of  structure.  We  ascend  the  lofty  peaks  of 
the  Cordillera  and  we  find  an  alpine  species  of  bizcacha;  we 
look  to  the  waters,  and  we  do  not  find  the  beaver  or  musk- 
rat,  but  the  coypu  and  capybara,  rodents  of  the  American 
type.  Innumerable  other  instances  could  be  given.  If  we 
look  to  the  islands  off  the  American  shore,  however  much  they 
may  differ  in  geological  structure,  the  inhabitants,  though 
they  may  be  all  peculiar  species,  are  essentially  American." 

What  is  the  generalization  implied  by  these  two  groups  of 
facts?  On  the  one  hand,  we  have  similarly-conditioned,  and 
sometimes  nearly-adjacent,  areas,  occupied  by  quite  different 
Faunas.  On  the  one  hand,  we  have  areas  remote  from  one 
another  in  latitude,  and  contrasted  in  soil  as  well  as  climate, 
occupied  by  closely-allied  Faunas.  Clearly  then,  as  like  or- 
ganisms are  not  universally,  or  even  generally,  found  in  like 
habitats,  nor  very  unlike  organisms  in  very  unlike  habitats, 
there  is  no  manifest  pre-determined  adaptation  of  the  organ- 
isms to  the  habitats.  The  organisms  do  no  occur  in  such 
and  such  places  solely  because  they  are  either  specially  fit  for 
those  places,  or  more  fit  for  them  than  all  other  organisms. 

The  induction  under  which  these  facts  come,  and  which 
unites  them  with  various  other  facts,  is  a  totally-different  one. 
When  we  see  that  the  similar  areas  peopled  by  dissimilar 
forms,  are  those  between  which  there  are  impassable  barriers ; 
while  the  dissimilar  areas  peopled  by  similar  forms,  are  those 
between  which  there  are  no  such  barriers ;  we  are  at  once  re- 
minded of  the  general  truth  exemplified  in  the  last  section — 
the  truth  that  each  species  of  organism  tends  ever  to  expand 
its  sphere  of  existence — to  intrude  on  other  areas,  other 
modes  of  life,  other  media.  And  we  are  shown  that  through 
these  perpetually-recurring  attempts  to  thrust  itself  into  every 


404  THE  INDUCTIONS  OP  BIOLOGY. 

accessible  habitat,  each  species  spreads  until  it  reaches  limits 
which  are  for  the  time  insurmountable. 

§  107.  We  pass  now  to  the  distribution  of  organic  forms  in 
Time.  Geological  inquiry  has  established  the  truth  that 
during  a  Past  of  immeasurable  duration,  plants  and  animals 
have  existed  on  the  Earth.  In  all  countries  their  buried 
remains  are  found  in  greater  or  less  abundance.  From  com- 
paratively small  areas  multitudinous  different  types  have  been 
exhumed.  Every  exploration  of  new  areas,  and  every  closer 
inspection  of  areas  already  explored,  brings  more  types  to 
light.  And  beyond  question,  an  exhaustive  examination  of 
all  exposed  strata,  and  of  all  strata  now  covered  by  the  sea, 
would  disclose  types  immensely  out-numbering  those  at 
present  known.  Further,  geologists  agree  that  even  had  we 
before  us  every  kind  of  fossil  which  exists,  we  should  still 
have  nothing  like  a  complete  index  to  the  past  inhabitants  of 
our  globe.  Many  sedimentary  deposits  have  been  so  altered 
by  the  heat  of  adjacent  molten  matter,  as  greatly  to  obscure  the 
organic  remains  contained  in  them.  The  extensive  formations 
once  called  "  transition,"  and  now  re-named  "  metamorphic," 
are  acknowledged  to  be  formations  of  sedimentary  origin,  from 
which  all  traces  of  such  fossils  as  they  probably  included  have 
been  obliterated  by  igneous  action.  And  the  accepted  con- 
clusion is  that  igneous  rock  has  everywhere  resulted  from 
the  melting-up  of  beds  of  detritus  originally  deposited  by 
water.  How  long  the  reactions  of  the  Earth's  molten  nucleus 
on  its  cooling  crust,  have  been  thus  destroying  the  records  of 
Life,  it  is  impossible  to  say ;  but  there  are  strong  reasons  for 
believing  that  the  records  which  remain  bear  but  a  small  ratio 
to  the  records  which  have  been  destroyed.  Thus  we  have 
but  extremely  imperfect  data  for  conclusions  respecting  the 
distribution  of  organic  forms  in  Time.  Some  few  generaliza- 
tions, however,  may  be  regarded  as  established. 

One  is  that  the  plants  and  animals  now  existing  mostly 
differ  from  the  plants  and  animals  which  have  existed- 


DISTRIBUTION.  405 

Though  there  are  species  common  to  our  present  Fauna  and 
to  past  Faunas,  yet  the  fades  of  our  present  Fauna  differs, 
more  or  less,  from  the  fades  of  each  past  Fauna.  On  carry- 
ing out  the  comparison,  we  find  that  past  Faunas  differ  from 
one  another,  and  that  the  differences  between  them  are  pro- 
portionate to  their  degrees  of  remoteness  from  one  another  in 
Time,  as  measured  by  their  relative  positions  in  the  sediment- 
ary series.  So  that  if  we  take  the  assemblage  of  organic 
forms  living  now,  and  compare  it  with  the  successive  assem- 
blages of  organic  forms  which  have  lived  in  successive  geologic 
epochs,  we  find  that  the  farther  we  go  back  into  the  past,  the 
greater  does  the  unlikeness  become.  The  number  of  species 
and  genera  common  to  the  compared  assemblages,  becomes 
smaller  and  smaller;  and  the  assemblages  differ  more  and 
more  in  their  general  characters.  Though  a  species  of 
brachiopod  now  extant  is  almost  identical  with  a  species 
found  in  Silurian  strata,  though  between  the  Silurian  Fauna 
and  our  own  there  are  sundry  common  genera  of  molluscs, 
yet  it  is  undeniable  that  there  is  a  proportion  between  lapse 
of  time  and  divergence  of  organic  forms. 

This  divergence  is  comparatively  slow  and  continuous 
where  there  is  continuity  in  the  geological  formations,  but  is 
sudden,  and  comparatively  wide,  wherever  there  occurs  a 
great  break  in  the  succession  of  strata.  The  contrasts  which 
thus  arise,  gradually  or  all  at  once,  in  formations  that  are 
continuous  or  discontinuous,  are  of  two  kinds.  Faunas  of 
different  eras  are  distinguished  partly  by  the  absence  from 
the  one  of  type's  present  in  the  other,  and  partly  by  the 
unlikenesses  between  the  types  common  to  both.  Such  con- 
trasts between  Faunas  as  are  due  to  the  appearance  or  disap- 
pearance of  types,  are  of  secondary  significance :  they  possibly, 
or  probably,  do  not  imply  anything  more  than  migrations  or 
extinctions.  The  most  significant  contrasts  are  those  between 
successive  groups  of  organisms  of  the  same  type.  And 
among  such,  as  above  said,  the  differences  are,  speaking 
generally,  small  and  continuous  where  a  series  of  conformable 
27 


406  THE  INDUCTIONS  OF  BIOLOGY. 

strata  gives  proof  of  continued  existence  of  the  type  in  the 
locality ;  while  they  are  comparatively  large  and  abrupt  where 
the  adjacent  formations  are  shown  to  have  been  separated 
by  long  intervals. 

Another  general  fact,  referred  to  by  Mr.  Darwin  as  one 
which  paleontology  has  made  tolerably  certain,  is  that  forms 
and  groups  of  forms  which  have  once  disappeared  from  the 
Earth,  do  not  reappear.  Passing  over  the  few  species  which 
have  continued  throughout  the  whole  period  geologically 
recorded,  it  may  be  said  that  each  species  after  arising,  spread- 
ing for  an  era,  and  continuing  abundant  for  an  era,  eventually 
declines  and  becomes  extinct;  and  that  similarly,  each  genus 
during  a  longer  period  increases  in  the  number  of  its  species, 
and  during  a  longer  period  dwindles  and  at  last  dies  out. 
After  making  its  exit  neither  species  nor  genus  ever  re-enters. 
The  like  is  true  even  of  those  larger  groups  called  orders. 
Four  types  of  reptiles  which  were  once  abundant  have  not 
been  found  in  modern  formations,  and  do  not  at  present  exist. 
Though  nothing  less  than  an  exhaustive  examination  of  all 
strata,  can  prove  conclusively  that  a  type  of  organization 
when  once  lost  is  never  reproduced,  yet  so  many  facts  point 
to  this  inference  that  its  truth  can  scarcely  be  doubted. 

To  frame  a  conception  of  the  total  amount  and  general 
direction  of  the  change  in  organic  forms  during  the  time 
measured  by  our  sedimentary  series,  is  at  present  impossible — 
the  data  are  insufficient.  The  immense  contrast  between  the 
few -and  low  forms  of  the  earliest-known  Fauna,  and  the 
many  and  high  forms  of  our  existing  Fauna,  has  been  com- 
monly supposed  to  prove,  not  only  great  change  but  great 
progress.  Nevertheless,  this  appearance  of  progress  may  be, 
and  probably  is,  mainly  illusive.  Wider  knowledge  has  shown 
that  remains  of  comparatively  well-organized  creatures  really 
existed  in  strata  long  supposed  to  be  devoid  of  them,  and 
that  where  they  are  absent,  the  nature  of  the  strata  often 
explains  their  absence,  without  assuming  that  they  did  not 
exist  when  these  strata  were  formed.  It  is  a  tenable 


DISTRIBUTION.  407 

hypothesis  that  the  successively-higher  types  fossilized  in  our 
successively-later  deposits,  indicate  nothing  more  than  suc- 
cessive migrations  from  pre-existing  continents  to  continents 
that  were  step  by  step  emerging  from  the  ocean — migrations 
which  necessarily  began  with  the  inferior  orders  of  organ- 
isms, and  included  the  successively-superior  orders  as  the 
new  lands  became  more  accessible  to  them  and  better  fitted 
for  them.* 

While  the  evidence  usually  supposed  to  prove  progression  is 
thus  untrustworthy,  there  is  trustworthy  evidence  that  there 
has  been,  in  many  cases,  little  or  no  progression.  Though  the 
orders  which  have  existed  from  paleozoic  and  mesozoic  times 
down  to  the  present  day,  are  almost  universally  changed,  yet 
a  comparison  of  ancient  and  modern  members  of  these  orders 
shows  that  the  total  amount  of  change  is  not  relatively  great, 
and  that  it  is  not  manifestly  towards  a  higher  organization. 
Though  nearly  all  the  living  forms  which  have  prototypes  in 
early  formations  differ  from  these  prototypes  specially,  and 
in  most  cases  generically,  yet  ordinal  peculiarities  are,  in  nu- 
merous cases,  maintained  from  the  earliest  times  geologically 
recorded,  down  to  our  own  time;  and  we  have  no  visible  evi- 
dence of  superiority  in  the  existing  genera  of  these  orders.  In 

*  For  explanations,  see  "  Illogical  Geology."  Essays,  Vol.  I.  How  much 
we  may  be  misled  by  assuming  that  because  the  remains  of  creatures  of  high 
types  have  not  been  found  in  early  strata,  such  creatures  did  not  exist  when 
those  strata  were  formed,  has  recently  (1897)  been  shown  by  the  discovery 
of  a  fossil  Sea-cow  in  the  lower  Miocene  of  Hesse-Darmstadt.  The  skeleton 
of  this  creature  proves  that  it  differed  from  such  Sirenian  mammals  as  the 
existing  Manatee  only  in  very  small  particulars:  further  dwindling  of  dis- 
used parts  being  an  evident  cause.  If,  now,  we  consider  that  since  the 
beginning  of  Miocene  days  this  aberrant  type  of  mammal  has  not  much 
increased  its  divergence  from  the  ordinary  mammalian  type ;  if  we  then 
consider  how  long  it  must  have  taken  for  this  large  aquatic  mammal  (some 
eight  or  ten  feet  long)  to  be  derived  by  modification  from  a  land-mammal ; 
and  if  then  we  contemplate  the  probable  length  of  the  period  required  for  the 
evolution  of  that  land-mammal  out  of  a  pre-mammalian  type ;  we  seem  car- 
ried back  in  thought  to  a  time  preceding  any  of  our  geologic  records.  We 
are  shown  that  the  process  of  organic  evolution  has  most  likely  been  far 
slower  than  is  commonly  supposed. 


408  THE  INDUCTIONS  OP  BIOLOGY. 

his  lecture  "  On  the  Persistent  Types  of  Animal  Life,"  Prof. 
Huxley  enumerated  many  cases.  On  the  authority  of  Dr. 
Hooker  he  stated  "  that  there  are  Carboniferous  plants  which 
appear  to  be  generically  identical  with  some  now  living :  that 
the  cone  of  the  Oolitic  Araucaria  is  hardly  distinguishable 
from  that  of  an  existing  species;  that  a  true  Pinus  appears 
in  the  Purbecks  and  a  Juglans  in  the  chalk."  Among  animals 
he  named  palaeozoic  and  mesozoic  corals  which  are  very  like 
certain  extant  corals ;  genera  of  Silurian  molluscs  that  answer 
to  existing  genera;  insects  and  arachnids  in  the  coal-forma- 
tions that  are  not  more  than  generically  distinct  from  some  of 
our  own  insects  and  arachnids.  He  instanced  "  the  Devonian 
and  Carboniferous  Pleuracanthus,  which  differs  no  more  from 
existing  sharks  than  these  do  from  one  another ; "  early 
mesozoic  reptiles  "  identical  in  the  essential  characters  of  their 
organization  with  those  now  living ;  "  and  Triassic  mammals 
which  did  not  differ  "  nearly  so  much  from  some  of  those 
which  now  live,  as  these  differ  from  one  another."  Continu- 
ing the  argument  in  his  "Anniversary  Address  to  the 
Geological  Society  "  in  1862,  Prof.  Huxley  gave  many  cases 
in  which  the  changes  that  have  taken  place,  are  not  changes 
towards  a  more  specialized  or  higher  organization — asking 
"in  what  sense  are  the  Liassic  Chelonia  inferior  to  those 
which  now  exist?  How  are  the  Cretaceous  Ichthyosauria, 
Plesiosauria,  or  Pterosauria  less  embryonic  or  more  differenti- 
ated species  than  those  of  the  Lias  ?  "  While,  however,  con- 
tending that  in  most  instances  "positive  evidence  fails  to 
demonstrate  any  sort  of  progressive  modification  towards  a  less 
embryonic  or  less  generalized  type  in  a  great  many  groups  of 
animals  of  long-continued  geological  existence,"  Prof.  Huxley 
added  that  there  are  other  groups,  "  co-existing  with  them 
under  the  same  conditions,  in  which  more  or  less  distinct 
indications  of  such  a  process  seem  to  be  traceable."  And 
in  illustration  of  this,  he  named  that  better  development 
of  the  vertebra?  which  characterizes  some  of  the  more 
modern  fishes  and  reptiles,  when  compared  with  ancient  fishes 


DISTRIBUTION.  409 

and  reptiles  of  the  same  orders ;  and  the  "  regularity  and 
evenness  of  the  dentition  of  the  Anoploiherium  as  contrasting 
with  that  of  existing  Artiodactyles."  * 

The  facts  thus  summed  up  do  not  show  that  higher  forms 
have  not  arisen  in  the  course  of  geologic  time,  any  more  than 
the  facts  commonly  cited  prove  that  higher  forms  have  arisen ; 
nor  are  they  regarded  by  Professor  Huxley  as  showing  this. 
Were  those  which  have  survived  from  palaeozoic  and  mesozoic 
days  down  to  our  own  day,  the  only  types;  and  did  the 
modifications,  rarely  of  more  than  generic  value,  which  these 
types  have  undergone,  give  no  better  evidences  of  increased 
complexity  than  are  actually  given  by  them ;  then  it  would  be 
inferable  that  there  has  been  no  appreciable  advance.  But 
there  now  exist,  and  have  existed  during  the  more  recent 
geologic  epochs,  various  types  which  are  not  known  to  have 
existed  in  earlier  epochs — some  of  them  widely  unlike  these 
persistent  types  and  some  of  them  nearly  allied  to  these 
persistent  types.  As  yet,  we  know  nothing  about  the  origins 
of  these  new  types.  But  it  is  possible  that  causes  like  those 
which  have  produced  generic  differences  in  the  persistent 
types,  have,  in  some  or  many  eases,  produced  modifications 
great  enough  to  constitute  ordinal  differences.  If  structural 
contrasts  not  exceeding  certain  moderate  limits  are  held  to 
mark  only  generic  distinctions;  and  if  organisms  displaying 
larger  contrasts  are  regarded  as  ordinally  or  typically  distinct ; 
it  is  obvious  that  the  persistence  of  a  given  type  through  a 
long  geologic  period  without  apparently  undergoing  devia- 
tions of  more  than  generic  value,  by  no  means  disproves  the 
occurrence  of  far  greater  deviations  in  other  cases;  since 

*  Since  this  passage  was  written,  in  1863,  there  has  come  to  light  much 
more  striking  evidence  of  change  from  a  more  generalized  to  a  less  general- 
ized type  during  geologic  time.  In  a  lecture  delivered  by  him  in  1876,  Prof. 
Huxley  gave  an  account  of  the  successive  modifications  of  skeletal  structure 
in  animals  allied  to  the  horse.  Beginning  with  the  Orohippus  of  the  Eocene 
formation,  which  had  four  complete  toes  on  the  front  limb  and  three  toes  on 
the  hind  limb,  he  pointed  out  the  successive  steps  by  which  in  the  Mesohippm, 
Jfiohippus,  Protohippus,  and  Pliohippus,  there  was  a  gradual  approach  to  the 
existing  horse. 


410  THE  INDUCTIONS  OP  BIOLOGY. 

the  forms  resulting  from  such  far  greater  deviations,  being 
regarded  as  typically  distinct  forms,  will  not  be  taken  as 
evidence  of  great  change  in  an  original  type.  That  which 
Prof.  Huxley's  argument  proves,  and  that  only  which  he 
considers  it  to  prove,  is  that  organisms  have  no  innate 
tendencies  to  assume  higher  forms ;  arid  that  "  any  admissible 
hypothesis  of  progressive  modification,  must  be  compatible 
with  persistence  without  progression  through  indefinite 
periods." 

One  very  significant  fact  must  be  added  concerning  the 
relation  between  distribution  in  Time  and  distribution  in 
Space.  I  quote  it  from  Mr.  Darwin : — "  Mr.  Clift  many  years 
ago  showed  that  the  fossil  mammals  from  the  Australian 
caves  were  closely  allied  to  the  living  marsupials  of  that  con- 
tinent. In  South  America  a  similar  relationship  is  manifest, 
even  to  an  uneducated  eye,  in  the  gigantic  pieces  of  armour 
like  those  of  the  armadillo,  found  in  several  parts  of  La  Plata ; 
and  Professor  Owen  has  shown  in  the  most  striking  manner 
that  most  of  the  fossil  mammals,  buried  there  in  such  num- 
bers, are  related  to  the  South  American  types.  This  relation- 
ship is  even  more  clearly  seen  in  the  wonderland  collection  of 
fossil  bones  made  by  MM.  Lund  and  Clausen  in  the  caves  of 
Brazil.  I  was  so  much  impressed  with  these  facts  that  I 
strongly  insisted,  in  1839  and  1845,  on  this  '  law  of  the  suc- 
cession of  types,' — on  '  this  wonderful  relationship  in  the 
same  continent  between  the  dead  and  the  living.'  Professor 
Owen  has  subsequently  extended  the  same  generalization  to 
the  Mammals  of  the  Old  World.  We  see  the  same  law  in 
this  author's  restorations  of  the  extinct  and  gigantic  birds  of 
New  Zealand.  We  see  it  also  in  the  birds  of  the  caves  of 
Brazil.  Mr.  Woodward  has  shown  that  the  same  laW  holds 
good  with  sea-shells,  but  from  the  wide  distribution  of  most 
genera  of  molluscs,  it  is  not  well  displayed  by  them.  Other 
cases  could  be  added,  as  the  relation  between  the  extinct 
and  living  landshells  of  Madeira,  and  between  the  extinct 
and  living  brackish-water  shells  of  the  Aralo-Caspian  Sea." 


DISTRIBUTION.  411 

The  general  results,  then,  are  these.  Our  knowledge  of 
distribution  in  Time,  being  derived  wholly  from  the  evidence 
afforded  by  fossils,  is  limited  to  that  geologic  time  of  which 
some  records  remain — cannot  extend  to  those  remoter  times 
the  records  of  which  have  been  obliterated.  From  these  re- 
maining records,  which  probably  form  but  a  small  fraction 
of  the  whole,  the  general  facts  deducible  are  these: — That 
such  organic  types  as  have  lived  through  successive  epochs, 
have  almost  universally  undergone  modifications  of  specific 
and  generic  values — modifications  which  have  commonly  been 
great  in  proportion  as  the  period  has  been  long.  That  besides 
the  types  which  have  persisted  from  ancient  eras  down  to  our 
own  era,  other  types  have  from  time  to  time  made  their  ap- 
pearance in  the  ascending  series  of  strata — types  of  which 
some  are  lower  and  some  higher  than  the  types  previously 
recorded;  but  whence  these  new  types  came,  and  whether 
any  of  them  arose  by  divergence  from  the  previously-recorded 
types,  the  evidence  does  not  yet  enable  us  to  say.  That  in 
the  course  of  long  geologic  epochs  nearly  all  species,  most 
genera,  and  a  few  orders,  have  become  extinct;  and  that  a 
species,  genus,  or  order,  which  has  once  disappeared  from  the 
Earth  never  reappears.  And,  lastly,  that  the  Fauna  now 
occupying  each  separate  area  of  the  Earth's  surface  is  very 
nearly  allied  to  the  Fauna  which  existed  on  that  area  during 
recent  geologic  times. 

§  108.  Omitting  sundry  minor  generalizations,  the  exposi- 
tion of  which  would  involve  too  much  detail,  what  is  to  be 
said  of  these  major  generalizations  ? 

The  distribution  in  Space  cannot  be  said  to  imply  that  or- 
ganisms have  been  designed  for  their  particular  habitats  and 
placed  in  them ;  since,  besides  the  habitat  in  which  each  kind 
of  organism  is  found  there  are  commonly  other  habitats,  as 
good  or  better  for  it,  from  which  it  is  absent — habitats  to 
which  it  is  so  much  better  fitted  than  organisms  now  occupy- 
ing them?  that  it  extrudes  these  organisms  when  allowed  the 


412  THE  INDUCTIONS  OF  BIOLOGY. 

opportunity.  Neither  can  we  suppose  that  the  purpose  has 
been  to  establish  varieties  of  Floras  and  Faunas ;  since,  if  so, 
why  are  the  Floras  and  Faunas  but  little  divergent  in  widely- 
sundered  areas  between  which  migration  is  possible,  while 
they  are  markedly  divergent  in  adjacent  areas  between  which 
migration  is  impossible  ? 

Passing  to  distributions  in  Time,  there  arise  the  questions 
— why  during  nearly  the  whole  of  that  vast  period  geologically 
recorded  have  there  existed  none  of  those  highest  organic 
forms  which  have  now  overrun  the  Earth? — how  is  it  that 
we  find  no  traces  of  a  creature  endowed  with  large  capacities 
for  knowledge  and  happiness?  The  answer  that  the  Earth 
was  not,  in  remote  times,  a  fit  habitation  for  such  a  creature, 
besides  being  unwarranted  by  the  evidence,  suggests  the 
equally  awkward  question — why  during  untold  millions  of 
years  did  the  Earth  remain  fit  only  for  inferior  creatures? 
What,  again,  is  the  meaning  of  extinction  of  types?  To 
conclude  that  the  saurian  type  was  replaced  by  other  types  at 
the  beginning  of  the  tertiary  period,  because  it  was  not 
adapted  to  the  conditions  which  then  arose,  is  to  conclude 
that  it  could  not  be  modified  into  fitness  for  the  conditions; 
and  this  conclusion  is  at  variance  with  the  hypothesis  that 
creative  skill  is  shown  in  the  multiform  adaptations  of  one 
type  to  many  ends. 

What  interpretations  may  rationally  be  put  on  these  and 
other  general  facts  of  distribution  in  Space  and  Time,  will 
be  seen  in  the  next  division  of  this  work. 


PART   III. 
THE   EVOLUTION   OF   LIFE, 


CHAPTEE  I. 

PRELIMINARY. 

§  109.  IN  the  foregoing  Part,  we  have  contemplated  the 
most  important  of  the  generalizations  to  which  biologists 
have  been  led  by  observation  of  organisms;  as  well  as  some 
others  which  contemplation  of  the  facts  has  suggested  to  me. 
These  Inductions  of  Biology  have  also  been  severally  glanced 
at  on  their  deductive  sides;  for  the  purpose  of  noting  the 
harmony  existing  between  them  and  those  primordial  truths 
set  forth  in  First  Principles.  Having  thus  studied  the  lead- 
ing phenomena  of  life  separately,  we  are  prepared  for  study- 
ing them  as  an  aggregate,  with  the  view  of  arriving  at  the 
most  general  interpretation  of  them. 

There  is  an  ensemble  of  vital  phenomena  presented  by  each 
organism  in  the  course  of  its  growth,  development,  and  decay ; 
and  there  is  an  ensemble  of  vital  phenomena  presented  by  the 
organic  world  as  a  whole.  Neither  of  these  can  be  properly 
dealt  with  apart  from  the  other.  But  the  last  of  them  may 
be  separately  treated  more  conveniently  than  the  first.  What 
interpretation  we  put  on  the  facts  of  structure  and  function 
in  each  living  body,  depends  entirely  on  our  conception  of  the 
mode  in  which  living  bodies  in  general  have  originated.  To 
form  some  conclusion  respecting  this  mode — a  provisional  if 
not  a  permanent  conclusion — must  therefore  be  our  first 
step. 

We  have  to  choose  between  two  hypotheses — the  hypo- 
thesis of  Special  Creation  and  the  hypothesis  of  Evolution. 

415 


416  THE  EVOLUTION  OF  LIFE. 

Either  the  multitudinous  kinds  of  organisms  which  now  exist, 
and  the  far  more  multitudinous  kinds  which  have  existed 
during  past  geologic  eras,  have  been  from  time  to  time  separ- 
ately made;  or  they  have  arisen  by  insensible  steps,  through 
actions  such  as  we  see  habitually  going  on.  Both  hypotheses 
imply  a  Cause.  The  last,  certainly  as  much  as  the  first, 
recognizes  this  Cause  as  inscrutable.  The  point  at  issue  is, 
how  this  inscrutable  Cause  has  worked  in  the  production  of 
living  forms.  This  point,  if  it  is  to  be  decided  at  all,  is  to  be 
decided  only  by  examination  of  evidence.  Let  us  inquire 
which  of  these  antagonist  hypotheses  is  most  congruous  with 
established  facts. 


CHAPTEK  II. 

GENERAL    ASPECTS   OF    THE     SPECIAL-CREATION"- 
HYPOTHESIS.* 

§  110.  EARLY  ideas  are  not  usually  true  ideas.  Unde- 
veloped intellect,  be  it  that  of  an  individual  or  that  of  the 
race,  forms  conclusions  which  require  to  be  revised  and  re- 
revised,  before  they  reach  a  tolerable  correspondence  with 
realities.  Were  it  otherwise  there  would  be  no  discovery,  no 
increase  of  intelligence.  What  we  call  the  progress  of 
knowledge,  is  the  bringing  of  Thoughts  into  harmony  with 
Things;  and  it  implies  that  the  first  Thoughts  are  either 
wholly  out  of  harmony  with  Things,  or  in  very  incomplete 
harmony  with  them. 

If  illustrations  be  needed  the  history  of  every  science 
furnishes  them.  The  primitive  notions  of  mankind  as  to  the 
structure  of  the  heavens  were  wrong;  and  the  notions  which 
replaced  them  were  successively  less  wrong.  The  original 
belief  respecting  the  form  of  the  Earth  was  wrong ;  and  this 
wrong  belief  survived  through  the  first  civilizations.  The 
earliest  ideas  that  have  come  down  to  us  concerning  the 
natures  of  the  elements  were  wrong;  and  only  in  quite 
recent  times  has  the  composition  of  matter  in  its  various 
forms  been  better  understood.  The  interpretations  of  me- 
chanical facts,  of  meteorological  facts,  of  physiological  facts, 
were  at  first  wrong.  In  all  these  cases  men  set  out  with 

*  Several  of  the  arguments  used  in  this  chapter  and  in  that  which  follows 
it,  formed  parts  of  an  essay  on  "  The  Development  Hypothesis,"  originally 
published  in  1852. 

417 


418  THE   EVOLUTION  OF  LIFE. 

beliefs  which,  if  not  absolutely  false,  contained  but  small 
amounts  of  truth  disguised  by  immense  amounts  of  error. 

Hence  the  hypothesis  that  living  beings  resulted  from 
special  creations,  being  a  primitive  hypothesis,  is  probably  an 
untrue  hypothesis.  It  would  be  strange  if,  while  early  men 
failed  to  reach  the  truth  in  so  many  cases  where  it  is  com- 
paratively conspicuous,  they  reached  it  in  a  case  where  it  is 
comparatively  hidden. 

§  111.  Besides  the  improbability  given  to  the  belief  in 
special  creations,  by  its  association  with  mistaken  beliefs  in 
general,  a  further  improbability  is  given  to  it  by  its  associa- 
tion with  a  special  class  of  mistaken  beliefs.  It  belongs  to  a 
family  of  beliefs  which  have  one  after  another  been  destroyed 
by  advancing  knowledge;  and  is,  indeed,  almost  the  only 
member  of  the  family  surviving  among  educated  people. 

We  all  know  that  the  savage  thinks  of  each  striking  phe- 
nomenon, or  group  of  phenomena,  as  caused  by  some  separate 
personal  agent;  that  out  of  this  conception  there  grows  up 
a  polytheistic  conception,  in  which  these  minor  personalities 
are  variously  generalized  into  deities  presiding  over  different 
divisions  of  nature;  and  that  these  are  eventually  further 
generalized.  This  progressive  consolidation  of  causal  agencies 
may  be  traced  in  the  creeds  of  all  races,  and  is  far  from 
complete  in  the  creed  of  the  most  advanced  races.  The  un- 
lettered rustics  who  till  our  fields,  do  not  let  the  conscious- 
ness of  a  supreme  power  wholly  absorb  the  aboriginal  con- 
ceptions of  good  and  evil  spirits,  and  of  charms  or  secret 
potencies  dwelling  in  particular  objects.  The  earliest  mode 
of  thinking  changes  only  as  fast  as  the  constant  relations 
among  phenomena  are  established.  Scarcely  less 

familiar  is  the  truth,  that  while  accumulating  knowledge 
makes  these  conceptions  of  personal  causal  agents  gradually 
more  vague,  as  it  merges  them  into  general  causes,  it  also 
destroys  the  habit  of  thinking  of  them  as  working  after  the 
methods  of  personal  agents.  We  do  not  now,  like  Kepler, 


THE  SPECIAL-CREATION-HYPOTHESIS.  419 

assume  guiding  spirits  to  keep  the  planets  in  their  orbits. 
It  is  no  longer  the  universal  belief  that  the  sea  was  once  for 
all  mechanically  parted  from  the  dry  land;  or  that  the 
mountains  were  placed  where  we  see  them  by  a  sudden  cre- 
ative act.  All  but  a  narrow  class  have  ceased  to  suppose 
sunshine  and  storm  to  be  sent  in  some  arbitrary  succession. 
The  majority  of  educated  people  have  given  up  thinking  of 
epidemics  of  punishments  inflicted  by  an  angry  deity.  Nor 
do  even  the  common  people  regard  a  madman  as  one  pos- 
sessed by  a  demon.  That  is  to  say,  we  everywhere  see  fading 
away  the  anthropomorphic  conception  of  Cause.  In  one  case 
after  another,  is  abandoned  the  ascription  of  phenomena  to 
a  will  analogous  to  the  human  will,  working  by  methods 
analogous  to  human  methods. 

If,  then,  of  this  once-numerous  family  of  beliefs  the  im- 
mense majority  have  become  extinct,  we  may  not  unrea- 
sonably expect  that  the  few  remaining  members  of  the  family 
will  become  extinct.  One  of  these  is  the  belief  we  are  here 
considering — the  belief  that  each  species  of  organism  was 
specially  created.  Many  who  in  all  else  have  abandoned 
the  aboriginal  theory  of  things,  still  hold  this  remnant  of  the 
aboriginal  theory.  Ask  any  well-informed  man  whether  he 
accepts  the  cosmogony  of  the  Indians,  or  the  Greeks,  or 
the  Hebrews,  and  he  will  regard  the  question  as  next  to  an 
insult.  Yet  one  element  common  to  these  cosmogonies  he 
very  likely  retains:  not  bearing  in  mind  its  origin.  For 
whence  did  he  get  the  doctrine  of  special  creations  ?  Catechise 
him,  and  he  is  forced  to  confess  that  it  was  put  into  his  mind 
in  childhood,  as  one  portion  of  a  story  which,  as  a  whole,  he 
has  long  since  rejected.  Why  this  fragment  is  likely  to  be 
right  while  all  the  rest  is  wrong,  he-  is  unable  to  say.  May 
we  not  then  expect  that  the  relinquishment  of  all  other  parts 
of  this  story,  will  by  and  by  be  followed  by  the  relinquish- 
ment of  this  remaining  part  of  it  ? 

§  112.  The  belief  which  we  find  thus  questionable,  both 


420  THE  EVOLUTION  OP  LIFE. 

as  being  a  primitive  belief  and  as  being  a  belief  belonging 
an  almost-extinct  family,  is  a  belief  not  countenanced  by 
single  fact.  No  one  ever  saw  a  special  creation;  no  01 
ever  found  proof  of  an  indirect  kind  that  a  special  creatic 
had  taken  place.  It  is  significant,  as  Dr.  Hooker  remark 
that  naturalists  who  suppose  new  species  to  be  miraculous 
originated,  habitually  suppose  the  origination  to  occur  i 
some  region  remote  from  human  observation.  Wherever  tl 
order  of  organic  nature  is  exposed  to  the  view  of  zoologis 
and  botanists,  it  expels  this  conception;  and  the  conceptic 
survives  only  in  connexion  with  imagined  places,  where  tl 
order  of  organic  nature  is  unknown. 

Besides  being  absolutely  without  evidence  to  give  it  exte 
nal  support,  this  hypothesis  of  special  creations  cannot  su; 
port  itself  internally — cannot  be  framed  into  a  cohere] 
thought.  It  is  one  of  those  illegitimate  symbolic  conce 
tions  which  are  mistaken  for  legitimate  symbolic  conce 
tions  (First  Principles,  §  9),  because  they  remain  unteste 
Immediately  an  attempt  is  made  to  elaborate  the  idea  in 
anything  like  a  definite  shape,  it  proves  to  be  a  pseud-ide 
admitting  of  no  definite  shape.  Is  it  supposed  that  a  ne 
organism,  when  specially  created,  is  created  out  of  nothing 
If  so,  there  is  a  supposed  creation  of  matter;  and  the  ere 
tion  of  matter  is  inconceivable — implies  the  establishment  < 
a  relation  in  thought  between  nothing  and  something- 
relation  of  which  one  term  is  absent — an  impossible  rel 
tion.  Is  it  supposed  that  the  matter  of  which  the  new  o 
ganism  consists  is  not  created  for  the  occasion,  but  is  take 
out  of  its  pre-existing  forms  and  arranged  into  a  new  forn: 
If  so,  we  are  met  by  the  question — how  is  the  re-arrangemei 
effected?  Of  the  myriad  atoms  going  to  the  composition  < 
the  new  organism,  all  of  them  previously  dispersed  throu^ 
the  neighbouring  air  and  earth,  does  each,  suddenly  disci 
gaging  itself  from  its  combinations,  rush  to  meet  the  res 
unite  with  them  into  the  appropriate  chemical  compound 
and  then  fall  with  certain  others  into  its  appointed  place  i 


THE  SPECIAL-CREATION-HYPOTHESIS.  421 

the  aggregate  of  complex  tissues  and  organs?  Surely  thus 
to  assume  a  myriad  supernatural  impulses,  differing  in  their 
directions  and  amounts,  given  to  as  many  different  atoms,  is 
a  multiplication  of  mysteries  rather  than  the  solution  of  a 
mystery.  For  every  one  of  these  impulses,  not  being  the 
result  of  a  force  locally  existing  in  some  other  form,  implies 
the  creation  of  force;  and  the  creation  of  force  is  just  as 
inconceivable  as  the  creation  of  matter.  It  is  thus  with 
all  attempted  ways  of  representing  the  process.  The  old 
Hebrew  idea  that  God  takes  clay  and  moulds  a  new  creature, 
as  a  potter  moulds  a  vessel,  is  probably  too  grossly  an- 
thropomorphic to  be  accepted  by  any  modern  defender  of  the 
special-creation  doctrine.  But  having  abandoned  this  crude 
belief,  what  belief  is  he  prepared  to  substitute?  If  a  new 
organism  is  not  thus  produced,  then  in  what  way  is  one 
produced?  or  rather — in  what  way  does  he  conceive  a  new 
organism  to  be  produced?  We  will  not  ask  for  the  ascer- 
tained mode,  but  will  be  content  with  a  mode  which  can  be 
consistently  imagined.  No  such  mode,  however,  is  assign- 
able. Those  who  entertain  the  proposition  that  each  kind  of 
organism  results  from  a  divine  interposition,  do  so  because 
they  refrain  from  translating  words  into  thoughts.  They  do 
not  really  believe,  but  rather  believe  they  believe.  For  belief, 
properly  so  called,  implies  a  mental  representation  of  the 
thing  believed,  and  no  such  mental  representation  is  here 
possible. 

§  113.  If  we  imagine  mankind  to  be  contemplated  by 
some  being  as  short-lived  as  an  ephemeron,  but  possessing 
intelligence  like  our  own — if  we  imagine  such  a  being  study- 
ing men  and  women,  during  his  few  hours  of  life,  and 
speculating  as  to  the  mode  in  which  they  came  into  existence ; 
it  is  manifest  that,  reasoning  in  the  usual  way,  he  would 
suppose  each  man  and  woman  to  have  been  separately 
created.  No  appreciable  changes  of  structure  occurring  in 
any  of  them  during  the  time  over  Which  his  observa- 
23 


422  THE  EVOLUTION  OF  LIFE. 

tions  extended,  this  being  would  probably  infer  that  no 
changes  of  structure  were  taking  place,  or  had  taken  place; 
and  that  from  the  outset  each  man  and  woman  had  pos- 
sessed all  the  characters  then  visible — had  been  originally 
formed  with  them.  The  application  is  obvious.  A 

human  life  is  ephemeral  compared  with  the  life  of  a  species ; 
and  even  the  period  over  which  the  records  of  all  human 
lives  extend,  is  ephemeral  compared  with  the  life  of  a 
species.  There  is  thus  a  parallel  contrast  between  the  im- 
mensely-long series  of  changes  which  have  occurred  during 
the  life  of  a  species,  and  that  small  portion  of  the  series  open 
to  our  view.  And  there  is  no  reason  to  suppose  that  the  first 
conclusion  drawn  by  mankind  from  this  small  part  of  the 
series  visible  to  them,  is  any  nearer  the  truth  than  would  be 
the  conclusion  of  the  supposed  ephemeral  being  respecting 
men  and  women. 

This  analogy,  suggesting  as  it  does  how  the  hypothesis  of 
special  creations  is  merely  a  formula  for  our  ignorance,  raises 
the  question — What  reason  have  we  to  assume  special  crea- 
tions of  species  but  not  of  individuals;  unless  it  be  that  in 
the  case  of  individuals  we  directly  know  the  process  to  be 
otherwise,  but  in  the  case  of  species  do  not  directly  know  it 
to  be  otherwise?  Have  we  any  ground  for  concluding  that 
species  were  specially  created,  except  the  ground  that  we 
have  no  immediate  knowledge  of  their  origin?  And  does 
our  ignorance  of  the  manner  in  which  they  arose  warrant  us 
in  asserting  that  they  arose  by  special  creation? 

Another  question  is  suggested  by  this  analogy.  Those 
who,  in  the  absence  of  immediate  evidence  of  the  way  in 
which  species  arose,  assert  that  they  arose  not  in  a  natural 
way  allied  to  that  in  which  individuals  arise,  but  in  a  super- 
natural way,  think  that  by  this  supposition  they  honour  the 
Unknown  Cause  of  things;  and  they  oppose  any  antagonist 
doctrine  as  amounting  to  an  exclusion  of  divine  power  from 
the  world:-  -.But. if  divine  power  is  demonstrated  by  the 
separate  creation  of  each  species,  would  it  not  have  been  still 


THE  SPECIAL-CREATION-HYPOTHESIS.  423 

better  demonstrated  by  the  separate  creation  of  each  indivi- 
dual? Why  should  there  exist  this  process  of  natural  gene- 
sis? Why  should  not  omnipotence  have  been  proved  by  the 
supernatural  production  of  plants  and  animals  everywhere 
throughout  the  world  from  hour  to  hour?  Is  it  replied  that 
the  Creator  was  able  to  make  individuals  arise  from  one 
another  in  a  natural  succession,  but  not  to  make  species  thus 
arise?  This  is  to  assign  a  limit  to  power  instead  of  magni- 
fying it.  Either  it  was  possible  or  not  possible  to  create 
species  and  individuals  after  the  same  general  method.  To 
say  that  it  was  not  possible  is  suicidal  in  those  who  use  this 
argument;  and  if  it  was  possible,  it  is  required  to  say  what 
end  is  served  by  the  special  creation  of  species  which  would 
not  have  been  better  served  by  the  special  creation  of 
individuals.  Again,  what  is  to  be  thought  of  the  fact 

that  the  immense  majority  of  these  supposed  special  creations 
took  place  before  mankind  existed?  Those  who  think  that 
divine  power  is  demonstrated  by  special  creations,  have  to 
answer  the  question — to  wty>m  demonstrated?  Tacitly  or 
avowedly-,  they  regard  the  demonstrations  as  being  for  the 
benefit  of  mankind.  But  if  so,  to  what  purpose  were  the 
millions  of  these  demonstrations  which  took  place  on  the 
Earth  when  there  were  no  intelligent  beings  to  contemplate 
them  ?  Did  the  Unknowable  thus  demonstrate  his  power  to 
himself?  Few  will  have  the  hardihood  to  say  that  any  such 
demonstration  was  needful.  There  is  no  choice  but  to  regard 
them,  either  as  superfluous  exercises  of  power,  which  is  a 
derogatory  supposition,  or  as  exercises  of  power  that  were 
necessary  because  species  could  not  be  otherwise  produced, 
which  is  also  a  derogatory  supposition. 

§  1 13a.  Other  implications  concerning  the  divine  character 
must  be  recognized  by  those  who  contend  that  each  species 
arose  by  divine  fiat.  It  is  hardly  supposable  that  Infinite 
Power  is  exercised  in  trivial  actions  effecting  trivial  changes. 
Yet  the  organic  world  in  its  hundreds  of  thousands  of  species 


424  THE  EVOLUTION  OF  LIFE. 

shows  in  each  sub-division  multitudinous  forms  which,  though 
unlike  enough  to  be  classed  as  specifically  distinct,  diverge 
from  one  another  only  in  small  details  which  have  no  signifi- 
cance in  relation  to  the  life  led.  Sometimes  the  number  of 
specific  distinctions  is  so  great  that  did  they  result  from 
human  agency  we  should  call  them  whimsical. 

For  example,  in  Lake  Baikal  are  found  115  species  of  an 
amphipod,  Gammarus;  and  the  multiplicity  becomes  start- 
ling on  learning  that  this  number  exceeds  the  number  of  all 
other  species  of  the  genus :  various  as  are  the  conditions  to 
which,  throughout  the  rest  of  the  world,  the  genus  is  subject. 
Still  stranger  seems  the  superfluous  exercise  of  power  on 
examining  the  carpet  of  living  forms  at  the  bottom  of  the 
ocean.  Not  dwelling  on  the  immense  variety  of  creatures 
unlike  in  type  which  live  miles  below  the  surface  in  absolute 
darkness,  it  will  suffice  to  instance  the  Polyzoa  alone:  low 
types  of  animals  so  small  that  a  thousand  of  them  would 
not  cover  a  square  inch,  and  on  which,  nevertheless,  there  has 
beertj  according  to  the  view  we  are  considering,  an  exercise 
of  creative  skill  such  that  by  small  variations  of  structure 
more  than  350  species  have  been  produced ! 

Kindred  illustrations  are  furnished  by  the  fauna  of  caverns. 
Are  we  to  suppose  that  numerous  blind  creatures — crusta- 
ceans, myriapods,  spiders,  insects,  fishes — were  specially  made 
sightless  to  fit  them  for  the  Mammoth  Cave?  Or  what  shall 
we  say  of  tbs  Proteus,  a  low  amphibian  with  rudimentary 
eyes,  which  inhabits  certain  caves  in  Carniola,  Carinthia  and 
Dalmatia  and  is  not  found  elsewhere.  Must  we  conclude  that 
God  went  out  of  his  way  to  devise  an  animal  for  these  places  ? 

More  puzzling  still  is  a  problem  presented  to  the  special- 
creationist  by  a  batrachian  inhabiting  Central  Australia.  In 
a  region  once  peopled  by  numerous  animals  but  now  made 
unfit  by  continuous  droughts,  there  exists  a  frog  which,  when 
the  pools  are  drying  up,  fills  itself  with  water  and  burrowing 
in  the  mud  hibernates  until  the  next  rains ;  which  may  come 
in  a  year  or  may  be  delayed  for  two  years.  What  is  to  be 


THE  SPECIAL-CREATION-HYPOTHESIS.  425 

thought  of  this  creature  ?  Were  its  structure  and  the  accom- 
panying instinct  divinely  planned  to  fit  it  to  this  particular 
habitat  ? 

Many  such  questions  might  be  asked  which,  if  answered  as 
the  current  theory  necessitates,  imply  a  divine  nature  hardly 
like  that  otherwise  assumed. 

§  114.  Those  who  espouse  the  aboriginal  hypothesis  en- 
tangle themselves  in  yet  other  theological  difficulties.  This 
assumption  that  each  kind  of  organism  was  specially  de- 
signed, carries  with  it  the  implication  that  the  designer 
intended  everything  which  results  from  the  design.  There  is 
no  escape  from  the  admission  that  if  organisms  were  severally 
constructed  with  a  view  to  their  respective  ends,  then  the 
character  of  the  constructor  is  indicated  both  by  the  ends 
themselves,  and  the  perfection  or  imperfection  with  which 
the  organisms  are  fitted  to  them.  Observe  the  consequences. 

Without  dwelling  on  the  question  recently  raised,  why 
during  untold  millions  of  years  there  existed  on  the  Earth 
no  beings  endowed  with  capacities  for  wide  thought  and 
high  feeling,  we  may  content  ourselves  with  asking  why, 
at  present,  the  Earth  is  largely  peopled  by  creatures  which 
inflict  on  one  another  so  much  suffering?  Omitting  the 
human  race,  whose  defects  and  miseries  the  current  theology 
professes  to  account  for,  and  limiting  ourselves  to  the  lower 
creation,  what  must  we  think  of  the  countless  different  pain- 
inflicting  appliances  and  instincts  with  which  animals  are 
endowed?  Not  only  now,  and  not  only  ever  since  men  have 
lived,  has  the  Earth  been  a  scene  of  warfare  among  all 
sentient  creatures ;  but  paleontology  shows  us  that  from  the 
earliest  eras  geologically  recorded,  there  has  been  going  on 
this  universal  carnage.  Fossil  structures,  in  common  with 
the  structures  of  existing  animals,  show  us  elaborate  weapons 
for  destroying  other  animals.  We  have  unmistakable  proof 
that  throughout  all  past  time,  there  has  been  a  ceaseless 
devouring  of  the  weak  by  the  strong.  How  is  this  to 


426  THE  EVOLUTION  OP  LIFE. 

be ,  explained  ?  How  happens  it  that  animals  were  so 
designed  as  to  render  this  bloodshed  necessary?  How 
happens  it  that  in  almost  every  species  the  number  of 
individuals  annually  born  is  such  that  the  majority 
die  by  starvation  or  by  violence  before  arriving  at  ma- 
turity? Whoever  contends  that  each  kind  of  animal  was 
specially  designed,  must  assert  either  that  there  was  a  deli- 
berate intention  on  the  part  of  the  Creator  to  produce  these 
results,  or  that  there  was  an  inability  to  prevent  them. 
Which  alternative  does  he  prefer? — to  cast  an  imputation  on 
the  divine  character  or  to  assert  a  limitation  of  the  divine 
power  ?  It  is  useless  for  him  to  plead  that  the  destruction  of 
the  less  powerful  by  the  more  powerful,  is  a  means  of  pre- 
venting the  miseries  of  decrepitude  and  incapacity,  and 
therefore  works  beneficently.  For  even  were  the  chief  mor- 
tality among  the  aged  instead  of  among  the  young,  there 
would  still  arise  the  unanswerable  question — why  were  not 
animals  constructed  in  such  ways  as  to  avoid  these  evils? 
why  were  not  their  rates  of  multiplication,  their  degrees  of 
intelligence,  and  their  propensities,  so  adjusted  that  these 
sufferings  might  be  escaped?  And  if  decline  of  vigour  was 
a  necessary  accompaniment  of  age,  why  was  it  not  provided 
that  the  organic  actions  should  end  in  sudden  death,  when- 
ever they  fell  below  the  level  required  for  pleasurable  exist- 
ence? Will  any  one  who  contends  that  organisms  were 
specially  designed,  assert  that  they  could  not  have  been  so 
designed  as  to  prevent  suffering  ?  And  if  he  admits  that 
they  could  have  been  made  so  as  to  prevent  suffering,  will 
he  assert  that  the  Creator  preferred  making  them  in  such 
ways  as  to  inflict  suffering  ? 

Even  as  thus  presented  the  difficulty  is  sufficiently  great ; 
but  it  appears  immensely  greater  when  we  examine  the  facts 
more  closely.  So  long  as  we  contemplate  only  the  preying 
of  the  superior  on  the  inferior,  some  good  appears  to  b? 
extracted  from  the  evil — a  certain  amount  of  life  of  a  higher 
order,  is  supported  by  sacrificing  a  great  deal  of  life  of  a 


THE  SPECIAL-CREATION-HYPOTHESIS.  427 

lower  order.  So  long,  too,  as  we  leave  out  all  mortality  but 
that  which,  by  carrying  off  the  least  perfect  members  of  each 
species,  leaves  the  most  perfect  members  to  survive  and 
multiply;  we  see  some  compensating  benefit  reached  through 
the  suffering  inflicted.  But  what  shall  we  say  on  finding 
innumerable  cases  in  which  the  suffering  inflicted  brings  no 
compensating  benefit  ?  What  shall  we  say  when  we  see  the 
inferior  destroying  the  superior?  What  shall  we  say  on 
finding  elaborate  appliances  for  furthering  the  multiplication 
of  organisms  incapable  of  feeling,  at  the  expense  of  misery 
to  organisms  capable  of  happiness  ? 

Of  the  animal  kingdom  as  a  whole,  more  than  half  the 
species  are  parasites.  "  The  number  of  these  parasites," 
says  Prof.  Owen,  "  may  be  conceived  when  it  is  stated  that 
almost  every  known  animal  has  its  peculiar  species,  and 
generally  more  than  one,  sometimes  as  many  as,  or  even 
more  kinds  than,  infest  the  human  body."  This  parasitism 
begins  among  the  most  minute  creatures  and  pervades  the 
entire  animal  kingdom  from  the  lowest  to  the  highest.  Even 
Protozoa,  made  visible  to  us  only  by  the  microscope,  are 
infested,  as  is  Paramcecium  by  broods  of  Sphcerophrya;  while 
in  large  and  complex  animals  parasites  are  everywhere  present 
in  great  variety.  More  than  this  is  true.  There  are  para- 
sites upon  parasites — an  arrangement  such  that  those  which 
are  torturing  the  creatures  they  inhabit  are  themselves  tor- 
tured by  indwelling  creatures  still  smaller:  looking  like  an 
ingenious  accumulation  of  pains  upon  pains. 

But  passing  over  the  evils  thus  inflicted  on  animals  of  in- 
ferior dignity,  let  us  limit  ourselves  to  the  case  of  Man.  The 
Bothriocephalus  latus  and  the  Toenia  solium,  are  two  kinds  of 
tape- worm,  which  flourish  in  the  human  intestines;  produc- 
ing great  constitutional  disturbances,  sometimes  ending  in 
insanity;  and  from  the  germs  of  the  Tcenla,  when  carried 
into  other  parts  of  the  body,  arise  certain  partially-developed 
forms  known  as  Cysticerci,,  Echinococci,  and  Ccenuri,  which 
cause  disorganization  more  or  less  extensive  in  the  brain,  the 


428  THE  EVOLUTION  OF  LIFE. 

lungs,  the  liver,  the  heart,  the  eye,  &c.,  often  ending  fatally 
after  long-continued  suffering.  Five  other  parasites,  belong- 
ing to  a  different  class,  are  found  in  the  viscera  of  man — the 
Trichocephalus,  the  Oxyuris,  the  Strongylus  (two  species), 
the  Ancylostomum  and  the  Ascaris;  which,  beyond  that 
defect  of  nutrition  which  they  necessarily  cause,  sometimes 
induce  certain  irritations  that  lead  to  complete  demoraliza- 
tion. Of  another  class  of  entozoa,  belonging  to  the  sub- 
division Trematoda,  there  are  five  kinds  found  in  different 
organs  of  the  human  body — the  liver  and  gall-duct,  the 
portal  vein,  the  intestine,  the  bladder,  the  eye.  Then  we 
have  the  Trichina  spiralis,  which  passes  through  one  phase  of 
its  existence  imbedded  in  the  muscles  and  through  another 
phase  of  its  existence  in  the  intestine;  and  which,  by  the 
induced  disease  Trichinosis,  has  lately  committed  such  ra- 
vages in  Germany  as  to  cause  a  panic.  To  these  we  must 
add  the  Guinea-worm,  which  in  some  part  of  Africa  and 
India  makes  men  miserable  by  burrowing  in  their  legs;  and 
the  more  terrible  African  parasite  the  Bilharzia,  which  affects 
30  per  cent,  of  the  natives  on  the  east  coast  with  bleeding  of 
the  bladder.  From  entozoa,  let  us  pass  to  epizoa.  There  are 
two  kinds  of  Acarl,  one  of  them  inhabiting  the  follicles  of 
the  skin  and  the  other  producing  the  itch.  There  are  crea- 
tures that  bury  themselves  beneath  the  skin  and  lay  their 
eggs  there;  and  there  are  three  species  of  lice  which  infest 
the  surface  of  the  body.  Nor  is  this  all.  Besides  animal 
parasites  there  are  sundry  vegetal  parasites,  which  grow  and 
multiply  at  our  cost.  The  Sarcina  ventriculi  inhabits  the 
stomach,  and  produces  gastric  disturbance.  The  Leptothrix 
buccalis  is  extremely  general  in  the  mouth,  and  may  have 
something  to  do  with  the  decay  of  teeth.  And  besides  these 
there  are  microscopic  fungi  which  produce  ringworm,  porrigo, 
pityriasis,  thrush,  &c.  Thus  the  human  body  is  the 

habitat  of  parasites,  internal  and  external,  animal  and  ve- 
getal, numbering,  if  all  are  set  down,  between  two  and  three 
dozen  species;  sundry  of  which  are  peculiar  to  Man,  and 


THE  SPECIAL-CREATION-HYPOTHESIS.  429 

many  of  which  produce  great  suffering  and  not  unfrequently 
death.  What  interpretation  is  to  be  put  on  these  facts  'by 
those  who  espouse  the  hypothesis  of  special  creations?  Ac- 
cording to  this  hypothesis,  all  these  parasites  were  designed 
for  their  respective  modes  of  life.  They  were  endowed  with 
constitutions  fitting  them  to  live  by  absorbing  nutriment 
from  the  human  body;  they  were  furnished  with  appliances, 
often  of  a  formidable  kind,  enabling  them  to  root  themselves 
in  and  upon  the  human  body;  and  they  were  made  prolific 
in  an  almost  incredible  degree,  that  their  germs  might  have 
a  sufficient  number  of  chances  of  finding  their  way  into  the 
human  body.  In  short,  elaborate  contrivances  were  com- 
bined to  insure  the  continuance  of  their  respective  races; 
and  to  make  it  impossible  for  the  successive  generations  of 
men  to  avoid  being  preyed  on  by  them.  What  shall  we  say 
to  this  arrangement  ?  Shall  we  say  that  "  the  head  and 
crown  of  things,"  was  provided  as  a  habitat  for  these  para- 
sites? Shall  we  say  that  these  degraded  creatures,  incapable 
of  thought  or  enjoyment,  were  created  that  they  might  cause 
human  misery?  One  or  other  of  these  alternatives  must  be 
chosen  by  those  who  contend  that  every  kind  of  organism 
was  separately  devised  by  the  Creator.  Which  do  they 
prefer?  With  the  conception  of  two  antagonist  powers, 
which  severally  work  good  and  evil  in  the  world,  the  facts 
are  congruous  enough.  But  with  the  conception  of  a  supreme 
beneficence,  this  gratuitous  infliction  of  pain  is  absolutely 
incompatible. 

§  115.  See  then  the  results  of  our  examination.  The 
belief  in  special  creations  of  organisms  arose  among  men 
during  the  era  of  profoundest  darkness;  and  it  belongs  to  a 
family  of  beliefs  which  have  nearly  all  died  out  as  enlighten- 
ment has  increased.  It  is  without  a  solitary  established  fact 
on  which  to  stand;  and  when  the  attempt  is  made  to  put  it 
into  definite  shape  in  the  mind,  it  turns  out  to  be  only  a 
pseud-idea.  This  mere  verbal  hypothesis,  which  men  idly 


430  THE  EVOLUTION  OP  LIFE. 

accept  as  a  real  or  thinkable  hypothesis,  is  of  the  same 
nature  as  would  be  one,  based  on  a  day's  observation  of 
human  life,  that  each  man  and  woman  was  specially  created 
— an  hypothesis  not  suggested  by  evidence  but  by  lack  of 
evidence — an  hypothesis  which  formulates  ignorance  into  a 
semblance  of  knowledge.  Further,  we  see  that  this  hypo- 
thesis, failing  to  satisfy  men's  intellectual  need  of  an  inter- 
pretation, fails  also  to  satisfy  their  moral  sentiment.  It  is 
quite  inconsistent  with  those  conceptions  of  the  divine  nature 
which  they  profess  to  entertain.  If  infinite  power  was  to  be 
demonstrated,  then,  either  by  the  special  creation  of  every 
individual,  or  by  the  production  of  species  by  some  method 
of  natural  genesis,  it  would  be  better  demonstrated  than  by 
the  use  of  two  methods,  as  assumed  by  the  hypothesis.  And 
if  infinite  goodness  was  to  be  demonstrated,  then,  not  only 
do  the  provisions  of  organic  structure,  if  they  are  specially 
devised,  fail  to  demonstrate  it,  but  there  is  an  enormous 
mass  of  them  which  imply  malevolence  rather  than  bene- 
volence. 

Thus  the  hypothesis  of  special  creations  turns  out  to  be 
worthless  by  its  derivation;  worthless  in  its  intrinsic  in- 
coherence; worthless  as  absolutely  without  evidence;  worth- 
less as  not  supplying  an  intellectual  need;  worthless  as  not 
satisfying  a  moral  want.  We  must  therefore  consider  it  as 
counting  for  nothing,  in  opposition  to  any  other  hypothesis 
respecting  the  origin  of  organic  beings. 


CHAPTER  III. 

GENERAL   ASPECTS    OF   THE   EVOLUTION-HYPOTHESIS. 

§  116.  JUST  as  the  supposition  that  races  of  organisms 
have  been  specially  created,  is  discredited  by  its  origin;  so, 
conversely,  the  supposition  that  races  of  organisms  have 
been  evolved,  is  credited  by  its  origin.  Instead  of  being 
a  conception  suggested  and  accepted  when  mankind  were 
profoundly  ignorant,  it  is  a  conception  born  in  times  of  com- 
parative enlightenment.  Moreover,  the  belief  that  plants 
and  animals  have  arisen  in  pursuance  of  uniform  laws,  instead 
of  through  breaches  of  uniform  laws,  is  a  belief  which  has 
come  into  existence  in  the  most-instructed  class,  living  in 
these  better-instructed  times.  Not  among  those  who  have 
disregarded  the  order  of  Nature,  has  this  idea  made  its 
appearance;  but  among  those  who  have  familiarized  them- 
selves with  the  order  of  Nature.  Thus  the  derivation  of  this 
modern  hypothesis  is  as  favourable  as  that  of  the  ancient 
hypothesis  is  unfavourable. 

§  117.  A  kindred  antithesis  exists  between  the  two  fami- 
lies of  beliefs,  to  which  the  beliefs  we  are  comparing  severally 
belong.  While  the  one  family  has  been  dying  out  the  other 
family  has  been  multiplying.  As  fast  as  men  have  ceased  to 
regard  different  classes  of  phenomena  as  caused  by  special 
personal  agents,  acting  irregularly;  so  fast  have  they  corre 
to  regard  these  different  classes  of  phenomena  as  caused  by 
a  general  agency  acting  uniformly — the  two  changes  being 

481 


432  THE  EVOLUTION  OF  LIFE. 

correlatives.  And  as,  on  the  one  hand,  the  hypothesis  that 
each  species  resulted  from  a  supernatural  act,  having  lost 
nearly  all  its  kindred  hypotheses,  may  be  expected  soon  to 
die;  so,  on  the  other  hand,  the  hypothesis  that  each  species 
resulted  from  the  action  of  natural  causes,  being  one  of  an 
increasing  family  of  hypotheses,  may  be  expected  to  survive. 

Still  greater  will  the  probability  of  its  survival  and  estab- 
lishment appear,  when  we  observe  that  it  is  one  of  a 
particular  genus  of  hypotheses  which  has  been  rapidly  ex- 
tending. The  interpretation  of  phenomena  as  results  of 
Evolution,  has  been  independently  showing  itself  in  various 
fields  of  inquiry,  quite  remote  from  one  another.  The  sup- 
position that  the  Solar  System  has  been  evolved  out  of  dif- 
fused matter,  is  a  supposition  wholly  astronomical  in  its 
origin  and  application.  Geologists,  without  being  led  thereto 
by  astronomical  considerations,  have  been  step  by  step  ad- 
vancing towards  the  conviction  that  the  Earth  has  reached 
its  present  varied  structure  by  modification  upon  modifica- 
tion. The  inquiries  of  biologists  have  proved  the  falsity  of 
the  once  general  belief,  that  the  germ  of  each  organism  is  a 
minute  repetition  of  the  mature  organism,  differing  from  it 
only  in  bulk;  and  they  have  shown,  contrariwise,  that  every 
organism  advances  from  simplicity  to  complexity  through 
insensible  changes.  Among  philosophical  politicians,  there 
has  been  spreading  the  perception  that  the  progress  of  society 
is  an  evolution :  the  truth  that  "  constitutions  are  not  made 
but  grow,"  is  seen  to  be  a  part  of  the  more  general  truth  that 
societies  are  not  made  but  grow.  It  is  now  universally 
admitted  by  philologists  that  languages,  instead  of  being  arti- 
ficially or  supernaturally  formed,  have  been  developed.  And 
the  histories  of  religion,  of  science,  of  the  fine  arts,  of  the 
industrial  arts,  show  that  these  have  passed  through  stages 
as  unobtrusive  as  those  through  which  the  mind  of  a  child 
passes  on  its  way  to  maturity.  If,  then,  the  recognition  of 
evolution  as  the  law  of  many  diverse  orders  of  phenomena, 
has  been  spreading;  may  we  not  say  that  there  thence  arises 


THE  EVOLUTION-HYPOTHESIS.  433 

the  probability  that  evolution  will  presently  be  recognized  as 
the  law  of  the  phenomena  we  are  considering  ?  Each  further 
advance  of  knowledge  confirms  the  belief  in  the  unity  of 
Nature;  and  the  discovery  that  evolution  has  gone  on,  or  is 
going  on,  in  so  many  departments  of  Nature,  becomes  a 
reason  for  believing  that  there  is  no  department  of  Nature  in 
which  it  does  not  go  on. 

§  118.  The  hypotheses  of  Special  Creation  and  Evolution, 
are  no  less  contrasted  in  respect  of  their  legitimacy  as  hy- 
potheses. While,  as  we  have  seen,  the  one  belongs  to  that 
order  of  symbolic  conceptions  which  are  proved  to  be  illusive 
by  the  impossibility  of  realizing  them  in  thought ;  the  other 
is  one  of  those  symbolic  conceptions  which  are  more  or  less 
fully  realizable  in  thought.  The  production  of  all  organic 
forms  by  the  accumulation  of  modifications  and  of  diver- 
gences by  the  continual  addition  of  differences  to  differences, 
is  mentally  representable  in  outline,  if  not  in  detail.  Various 
orders  of  our  experiences  enable  us  to  conceive  the  process. 
Let  us  look  at  one  of  the  simplest. 

There  is  no  apparent  similarity  between  a  straight  line 
and  a  circle.  The  one  is  a  curve;  the  other  is  defined  as 
without  curvature.  The  one  encloses  a  space;  the  other 
will  not  enclose  a  space  though  produced  for  ever.  The  one 
is  finite ;  the  other  may  be  infinite.  Yet,  opposite  as  the  two 
are  in  their  characters,  they  may  be  connected  together  by  a 
series  of  lines  no  one  of  which  differs  from  the  adjacent  ones 
in  any  appreciable  degree.  Thus,  if  a  cone  be  cut  by  a  plane 
at  right  angles  to  its  axis  we  get  a  circle.  If,  instead  of 
being  perfectly  at  right  angles,  the  plane  subtends  with  the 
axis  an  angle  of  89°  59',  we  have  an  ellipse  which  no  human 
eye,  even  when  aided  by  an  accurate  pair  of  compasses,  can 
distinguish  from  a  circle.  Decreasing  the  angle  minute  by 
minute,  this  closed  curve  becomes  perceptibly  eccentric,  then 
manifestly. so,  and  by  and  by  acquires  so  immensely  elongated 
a  form  so  as  to  bear  no  recognizable  resemblance  to  a  circle. 


434  THE  EVOLUTION  OP  LIFE. 

By  continuing  this  process  the  ellipse  changes  insensibly  into 
a  parabola.  On  still  further  diminishing  the  angle,  the  para- 
bola becomes!  an  hyperbola.  And  finally,  if  the  cone  be 
made  gradually  more  obtuse,  the  hyperbola  passes  into  a 
straight  line  as  the  angle  of  the  cone  approaches  180°.  Here 
then  we  have  five  different  species  of  line — circle,  ellipse, 
parabola,  hyperbola,  and  straight  line — each  having  its  pecu- 
liar properties  and  its  separate  equation,  and  the  first  and 
last  of  which  are  quite  opposite  in  nature,  connected  together 
as  members  of  one  series,  all  producible  by  a  single  process  of 
insensible  modification. 

But  the  experiences  which  most  clearly  illustrate  the  pro- 
cess of  general  evolution,  are  our  experiences  of  special 
evolution,  repeated  in  every  plant  and  animal.  Each  organ- 
ism exhibits,  within  a  short  time,  a  series  of  changes  which, 
when  supposed  to  occupy  a  period  indefinitely  great,  and  to 
go  on  in  various  ways  instead  of  one  way,  give  us  a  tolerably 
clear  conception  of  organic  evolution  at  large.  In  an  indi- 
•  vidual  development,  we  see  brought  into  a  comparatively 
infinitesimal  time,  a  series  of  metamorphoses  equally  great 
with  each  of  those  which  the  hypothesis  of  evolution  assumes 
to  have  taken  place  during  immeasurable  geologic  epochs.  A 
tree  differs  from  a  seed  in  every  respect — in  bulk,  in  struc- 
ture, in  colour,  in  form,  in  chemical  composition.  Yet  is  the 
one  changed  in  the  course  of  a  few  years  into  the  other: 
changed  so  gradually,  that  at  no  moment  can  it  be  said — 
Now  the  seed  ceases  to  be  and  the  tree  exists.  What  can  be 
more  widely  contrasted  than  a  newly-born  child  and  the 
small,  semi-transparent,  gelatinous  spherule  constituting  the 
human  ovum?  The  infant  is  so  complex  in  structure  that  a 
cyclopedia  is  needed  to  describe  its  constituent  parts.  The 
germinal  vesicle  is  so  simple  that  it  may  be  defined  in  a  line. 
Nevertheless,  nine  months  suffice  to  develop  the  one  out  of 
the  other;  and  that,  too,  by  a  series  of  modifications  so 
small,  that  were  the  embryo  examined  at  successive  minutes, 
even  a  microscope  would  not  disclose  any  sensible  changes. 


THE  EVOLUTION-HYPOTHESIS.  435 

Aided  by  such  facts,  the  conception  of  general  evolution  may 
be  rendered  as  definite  a  conception  as  any  of  our  complex 
conceptions  can  be  rendered.  If,  instead  of  the  successive 
minutes  of  a  child's  foetal  life,  we  take  the  lives  of  successive 
generations  of  creatures — if  we  regard  the  successive  genera- 
tions as  differing  from  one  another  no  more  than  the  foetus 
differs  in  successive  minutes;  our  imaginations  must  indeed 
be  feeble  if  we  fail  to  realize  in  thought,  the  evolution  of  the 
most  complex  organism  out  of  the  simplest.  If  a  single  cell, 
under  appropriate  conditions,  becomes  a  man  in  the  space  of  a 
few  years;  there  can  surely  be  no  difficulty  in  understanding 
how,  under  appropriate  conditions,  a  cell  may,  in  the  course 
of  untold  millions  of  years,  give  origin  to  the  human  race. 

Doubtless  many  minds  are  so  unfurnished  with  those  ex- 
periences of  Nature  out  of  which  this  conception  is  built, 
that  they  find  difficulty  in  forming  it.  Looking  at  things 
rather  in  their  statical  than  in  their  dynamical  aspects,  they 
never  realize  the  fact  that,  by  small  increments  of  modifica- 
tion, any  amount  of  modification  may  in  time  be  generated. 
The  surprise  they  feel  on  finding  one  whom  they  last  saw  as 
a  boy,  grown  into  a  man,  becomes  incredulity  when  the 
degree  of  change  is  greater.  To  such,  the  hypothesis  that  by 
any  series  of  changes  a  protozoon  can  give  origin  to  a  mam- 
mal, seems  grotesque — as  grotesque  as  Galileo's  assertion  of 
the  Earth's  movement  seemed  to  his  persecutors;  or  as 
grotesque  as  the  assertion  of  the  Earth's  sphericity  seems  now 
to  the  New  Zealanders.  But  those  who  accept  a  literally- 
unthinkable  proposition  as  quite  satisfactory,  may  not  un- 
naturally be  expected  to  make  a  converse  mistake. 

§  119.  The  hypothesis  of  evolution  is  contrasted  with  the 
hypothesis  of  special  creations,  in  a  further  respect.  It  is 
not  simply  legitimate  instead  of  illegitimate,  because  repre- 
sentable  in  thought  instead  of  unrepresentable;  but  it  has 
the  support  of  some  evidence,  instead  of  being  absolutely  un- 
supported by  evidence.  Though  the  facts  at  present  assign- 


436  THE  EVOLUTION  OP  LIFE. 

able  in  direct  proof  that  by  progressive  modifications,  races  of 
organisms  which  are  apparently  distinct  from  antecedent 
races  have  descended  from  them,  are  not  sufficient;  yet  there 
are  numerous  facts  of  the  order  required.  Beyond  all  ques- 
tion unlikenesses  of  structure  gradually  arise  among  the 
members  of  successive  generations.  We  find  that  there  is 
going  on  a  modifying  process  of  the  kind  alleged  as  the 
source  of  specific  differences:  a  process  which,  though  slow, 
does,  in  time,  produce  conspicuous  changes — a  process  which, 
to  all  appearance,  would  produce  in  millions  of  years,  any 
amount  of  change. 

In  the  chapters  on  "Heredity"  and  "Variation,"  contained 
in  the  preceding  Part,  many  such  facts  were  given,  and  more 
might  be  added.  Although  little  attention  has  been  paid  to 
the  matter  until  recent  times,  the  evidence  already  collected 
shows  that  there  take  place  in  successive  generations,  altera- 
tions of  structure  quite  as  marked  as  those  which,  in  succes- 
sive short  intervals,  arise  in  a  developing  embryo — nay,  often 
much  more  marked ;  since,  besides  differences  due  to  changes 
in  the  relative  sizes  or  parts,  there  sometimes  arise  differ- 
ences due  to  additions  and  suppressions  of  parts.  The  struc- 
tural modification  proved  to  have  taken  place  since  organisms 
have  been  observed,  is  not  less  than  the  hypothesis  demands 
— bears  as  great  a  ratio  to  this  brief  period,  as  the  total 
amount  of  structural  change  seen  in  the  evolution  of  a  com- 
plex organism  out  of  a  simple  germ,  bears  to  that  vast  period 
during  which  living  forms  have  existed  on  the  Earth. 

We  have,  indeed,  much  the  same  kind  and  quantity  of 
direct  evidence  that  all  organic  beings  have  arisen  through 
the  actions  of  natural  causes,  which  we  have  that  all  the 
structural  complexities  of  the  Earth's  crust  have  arisen 
through  the  actions  of  natural  causes.  Between  the  known 
modifications  undergone  by  organisms,  and  the  totality  of 
modifications  displayed  in  their  structures,  there  is  no  greater 
disproportion  than  between  the  observed  geological  changes, 
and  the  totality  of  geological  changes  supposed  to  have  been 


THE  EVOLUTION-HYPOTHESIS.  437 

similarly  caused.  Here  and  there  are  sedimentary  deposits 
now  slowly  taking  place.  At  this  place  a  shore  has  been 
greatly  encroached  on  by  the  sea  during  recorded  times;  and 
at  another  place  an  estuary  has  become  shallower  within 
some  generations.  In  one  region  an  upheaval  is  going  on  at 
the  rate  of  a  few  feet  in  a  century;  while  in  another  region 
occasional  earthquakes  cause  slight  variations  of  level.  Ap- 
preciable amounts  of  denudation  by  water  are  visible  in  some 
localities;  and  in  other  localities  glaciers  are  detected  in  the 
act  of  grinding  down  the  rocky  surfaces  over  which  they 
glide.  But  these  changes  are  infinitesimal  compared  with 
the  aggregate  of  changes  to  which  the  Earth's  crust  testifies, 
even  in  its  still  extant  systems  of  strata.  If,  then,  the  small 
changes  now  being  wrought  on  the  Earth's  crust  by  natural 
agencies,  yield  warrant  for  concluding  that  by  such  agencies 
acting  through  vast  epochs,  all  the  structural  complexities  of 
the  Earth's  crust  have  been  produced;  do  not  the  small 
known  modifications  produced  in  races  of  organisms  by  natu- 
ral agencies,  yield  warrant  for  concluding  that  by  natural 
agencies  h*ave  been  produced  all  those  structural  complexities 
which  we  see  in  them  ? 

The  hypothesis  of  Evolution  then,  has  direct  support  from 
facts  which,  though  small  in  amount,  are  of  the  kind  required ; 
and  the  ratio  which  these  facts  bear  to  the  generalization 
based  on  them,  seems  as  great  as  is  the  ratio  between  facts  and 
generalization  which,  in  another  case,  produces  conviction. 

§  120.  Let  us  put  ourselves  for  a  moment  in  the  position  of 
those  who,  from  their  experiences  of  human  modes  of  action, 
draw  differences  respecting  the  mode  of  action  of  that  Ulti- 
mate Power  manifested  to  us  through  phenomena.  We  shall 
find  the  supposition  that  each  kind  of  organism  was  separately 
designed  and  put  together,  to  be  much  less  consistent  with 
their  professed  conception  of  this  Ultimate  Power,  than  is  the 
supposition  that  all  kinds  of  organisms  have  resulted  from 
one  unbroken  process.  Irregularity  of  method  is  a  mark  of 


438  THE  EVOLUTION  OP  LIFE. 

weakness.  Uniformity  of  method  is  a  mark  of  strength.  Con- 
tinual interposition  to  alter  a  pre-arranged  set  of  actions, 
implies  defective  arrangement  in  those  actions.  The  main- 
tenance of  those  actions,  and  the  working  out  by  them  of  the 
highest  results,  implies  completeness  of  arrangement.  If 
human  workmen,  whose  machines  as  at  first  constructed  re- 
quire perpetual  adjustment,  show  their  increasing  skill  by 
making  their  machines  self-adjusting;  then,  those  who  figure 
to  themselves  the  production  of  the  world  and  its  inhabitants 
by  a  "  Great  Artificer,"  must  admit  that  the  achievement  of 
this  end  by  a  persistent  process,  adapted  to  all  contingencies, 
implies  greater  skill  than  its  achievement  by  the  process  of 
meeting  the  contingencies  as  they  severally  arise. 

So,  too,  it  is  with  the  contrast  under  its  moral  aspect.  We 
saw  that  to  the  hypothesis  of  special  creations,  a  difficulty  is 
presented  by  the  absence  of  high  forms  of  life  during  im- 
measurable epochs  of  the  Earth's  existence.  But  to  the 
hypothesis  of  evolution,  absence  of  them  is  no  such  obstacle. 
Suppose  evolution,  and  this  question  is  necessarily  excluded. 
Suppose  special  creations,  and  this  question  can  have  no 
satisfactory  answer.  Still  more  marked  is  the  con- 

trast between  the  two  hypotheses,  in  presence  of  that  vast 
amount  of  suffering  entailed  on  all  orders  of  sentient  beings 
by  their  imperfect  adaptations  to  their  conditions  of  life,  and 
the  further  vast  amount  of  suffering  entailed  on  them  by 
enemies  and  by  parasites.  We  saw  that  if  organisms  were 
severally  designed  for  their  respective  places  in  Nature,  the 
inevitable  conclusion  is  that  these  innumerable  kinds  of  in- 
ferior organisms  which  prey  on  superior  organisms,  were  in- 
tended to  inflict  all  the  pain  and  mortality  which  results. 
But  the  hypothesis  of  evolution  involves  us  in  no  such 
dilemma.  Slowly,  but  surely,  evolution  brings  about  an  in-, 
creasing  amount  of  happiness.  In  all  forms  of  organization 
there  is  a  progressive  adaptation,  and  a  survival  of  the  most 
adapted.  If,  in  the  uniform  working  out  of  the  process, 
there  are  evolved  organisms  of  low  types  which  prey  on 


THE  EVOLUTION-HYPOTHESIS.  439 

those  of  higher  types,  the  evils  inflicted  form  but  a  deduction 
from  the  average  benefits.  The  universal  multiplication  of 
the  most  adapted  must  cause  the  spread  of  those  superior 
organisms  which,  in  one  way  or  other,  escape  the  invasions 
of  the  inferior;  and  so  tends  to  produce  a  type  less  liable  to 
the  invasions  of  'the  inferior.  Thus  the  evils  accompanying 
evolution  are  ever  being  self-eliminated.  Though  there  may 
arise  the  question — Why  could  they  not  have  been  avoided? 
there  does  not  arise  the  question — Why  were  they  deliber- 
ately inflicted  ?  Whatever  may  be  thought  of  them,  it  is  clear 
that  they  do  not  imply  gratuitous  malevolence. 

§  121.  In  all  respects,  then,  the  hypothesis  of  evolution 
contrasts  favourably  with  the  hypothesis  of  special  creation. 
It  has  arisen  in  comparatively-instructed  times  and  in  the 
most  cultivated  class.  It  is  one  of  those  beliefs  in  the  uni- 
form concurrence  of  phenomena,  which  are  gradually  sup- 
planting beliefs  in  their  irregular  and  arbitrary  concurrence ; 
and  it  belongs  to  a  genus  of  these  beliefs  which  has  of  late 
been  rapidly  spreading.  It  is  a  definitely-conceivable  hypo- 
thesis; being  simply  an  extensio^n  to  the  organic  world  at 
large,  of  a  conception  framed  from  our  experiences  of  indi- 
vidual organisms;  just  as  the  hypothesis  of  universal  gravi- 
tation was  an  extension  of  the  conception  which  our  experi- 
ences of  terrestrial  gravitation  had  produced.  This  definitely- 
conceivable  hypothesis,  besides  the  support  of  numerous 
analogies,  has  the  support  of  direct  evidence.  We  have  proof 
that  there  is  going  on  a  process  of  the  kind  alleged;  and 
though  the  results  of  this  process,  as  actually  witnessed,  are 
minute  in  comparison  with  the  totality  of  results  ascribed 
to  it,  yet  they  bear  to  such  totality  a  ratio  as  great  as  that 
by  which  an  analogous  hypothesis  is  justified.  Lastly,  that 
sentiment  which  the  doctrine  of  special  creations  is  thought 
necessary  to  satisfy,  is  much  better  satisfied  by  the  doctrine  of 
evolution;  since  this  doctrine  raises  no  contradictory  impli- 


440  THE  EVOLUTION  OF  LIFE. 

cations  respecting  the  Unknown  Cause,  such  as  are  raised  by 
the  antagonist  doctrine. 

And  now,  having  observed  how,  under  its  most  general 
aspects,  the  hypothesis  of  organic  evolution  commends  itself 
to  us  by  its  derivation,  by  its  coherence,  by  its  analogies,  by 
its  direct  evidence,  by  its  implications;  let  us  go  on  to  con- 
sider the  several  orders  of  facts  which  yield  indirect  support 
to  it.  We  will  begin  by  noting  the  harmonies  between  it 
and  sundry  of  the  inductions  set  forth  in  Part  II. 


CHAPTER  IV. 

THE    ARGUMENTS    FROM    CLASSIFICATION. 

§  122.  IN  §  103,  we  saw  that  the  relations  which  exist 
among  the  species,  genera,  orders,  and  classes  of  organisms, 
are  not  interpretable  as  results  of  any  such  causes  as  have 
usually  been  assigned.  We  will  here  consider  whether  they 
are  interpretable  as  the  results  of  evolution.  Let  us  first  con- 
template some  familiar  facts. 

The  Norwegians,  Swedes,  Danes,  Germans,  Dutch,  and 
Anglo-Saxons,  form  together  a  group  of  Scandinavian  races, 
which  are  but  slightly  divergent  in  their  characters.  Welsh, 
Irish,  and  Highlanders,  though  they  have  differences,  hsve 
not  such  differences  as  hide  a  decided  community  of  nature: 
they  are  classed  together  as  Celts.  Between  the  Scandi- 
navian race  as  a  whole  and  the  Celtic  race  as  a  whole,  there 
is  a  distinction  greater  than  that  between  the  sub-divisions 
which  make  up  the  one  or  the  other.  Similarly,  the  several 
peoples  inhabiting  Southern  Europe  are  more  nearly  allied  to 
one  another,  than  the  aggregate  they  form  is  allied  to  the 
aggregates  of  Northern  peoples.  If,  again,  we  compare  these 
European  varieties  of  Man,  taken  as  a  group,  with  that  group 
of  Eastern  varieties  which  had  a  common  origin  with  it,  we 
see  a  stronger  contrast  than  between  the  groups  of  Euro- 
pean varieties  themselves.  And  once  more,  ethnologists  find 
differences  of  still  higher  importance  between  the  Aryan 
stock  as  a  whole  and  the  Mongolian  stock  as  a  whole,  or  the 

441 


442  THE  EVOLUTION  OF  LIFE. 

Negro  stock  as  a  whole.  Though  these  contrasts  are  partially 
obscured  by  intermixtures,  they  are  not  so  much  obscured 
as  to  hide  the  truths  that  the  most-nearly-allied  varieties  of 
Man  are  those  which  diverged  from  one  another  at  com- 
paratively-recent periods;  that  each  group  of  nearly-allied 
varieties  is  more  strongly  contrasted  with  other  such  groups 
that  had  a  common  origin  with  it  at  a  remoter  period;  and 
so  on  until  we  come  to  the  largest  groups,  which  are  the 
most  strongly  contrasted,  and  of  whose  divergence  no  trace  is 
extant. 

The  relations  existing  among  the  classes  and  sub-classes 
of  languages,  have  been  briefly  referred  to  by  Mr.  Darwin  in 
illustration  of  his  argument.  We  know  that  languages  have 
arisen  by  evolution.  Let  us  then  see  what  grouping  of  them 
evolution  has  produced.  On  comparing  the  dialects  of  adja- 
cent counties  in  England,  we  find  that  their  differences  are  so 
small  as  scarcely  to  distinguish  them.  Between  the  dialects 
of  the  Northern  counties  taken  together,  and  those  of  the 
Southern  counties  taken  together,  the  contrast  is  stronger. 
These  clusters  of  dialects,  together  with  those  of  Scotland  and 
Ireland,  are  nevertheless  so  similar  that  we  regard  them  as 
one  language.  The  several  languages  of  Scandinavian  Europe, 
including  English,  are  much  more  unlike  one  another  than 
are  the  several  dialects  which  each  of  them  includes;  in  cor- 
respondence with  the  fact  that  they  diverged  from  one 
another  at  earlier  periods  than  did  their  respective  dialects. 
The  Scandinavian  languages  have  nevertheless  a  certain  com- 
munity of  character,  distinguishing  them  as  a  group  from  the 
languages  of  Southern  Europe;  between  which  there  are 
general  and  special  affinities  that  similarly  unite  them  into  a 
group  formed  of  sub-groups  containing  sub-sub-groups.  And 
this  wider  divergence  between  the  order  of  languages  spoken 
"in  Northern  Europe  and  the  order  of  languages  spoken  in 
Southern  Europe,  answers  to  the  longer  time  that  has  elapsed 
since  their  differentiation  commenced.  Further,  these  two 
orders  of  modern  European  languages,  as  well  as  Latin  and 


THE  ARGUMENTS  FROM  CLASSIFICATION.          443 

Greek  and  certain  extinct  and  spoken  languages  of  the  East, 
are  shown  to  have  traits  in  common  which  unite  them  into 
one  great  class  known  as  Aryan  languages;  radically  dis- 
tinguished from  the  classes  of  languages  spoken  by  the  other 
main  divisions  of  the  human  race. 

§  123.  Now  this  kind  of  subordination  of  groups  which  we 
see  arises  in  the  course  of  continuous  descent,  multiplication, 
and  divergence,  is  just  the  kind  of  subordination  of  groups 
which  plants  and  animals  exhibit:  it  is  just  the  kind  of 
subordination  which  has  thrust  itself  on  the  attention  of 
naturalists  in  spite  of  pre-conceptions. 

The  original  idea  was  that  of  arrangement  in  linear  order. 
We  saw  that  even  after  a  considerable  acquaintance  with  the 
structures  of  organisms  had  been  acquired,  naturalists  con- 
tinued their  efforts  to  reconcile  the  facts  with  the  notion  of  a 
uni-serial  succession.  The  accumulation  of  evidence  necessi- 
tated the  breaking  up  of  the  imagined  chain  into  groups  and 
sub-groups.  Gradually  there  arose  the  conviction  that  these 
groups  do  not  admit  of  being  placed  in  a  line.  And  the  con- 
ception finally  arrived  at,  is  that  of  certain  great  sub-king- 
doms, very  widely  divergent,  each  made  up  of  classes  much 
less  divergent,  severally  containing  orders  still  less  divergent ; 
and  so  on  with  genera  and  species. 

Hence  this  "  grand  fact  in  natural  history  of  the  subordi- 
nation of  group  under  group,  which  from  its  familiarity  does 
not  always  sufficiently  strike  us,"  is  perfectly  in  harmony 
with  the  hypothesis  of  evolution.  The  extreme  significance 
of  this  kind  of  relation  among  organic  forms  is  dwelt  on  by 
Mr.  Darwin,  who  shows  how  an  ordinary  genealogical  tree 
represents,  on  a  small  scale,  a  system  of  grouping  analogous 
to  that  which  exists  among  organisms  in  general,  and  which  is 
explained  on  the  supposition  of  a  genealogical  tree  by  which 
all  organisms  are  affiliated.  If,  wherever  we  can  trace  direct 
descent,  multiplication,  and  divergence,  this  formation  of 
groups  within  groups  takes  place;  there  results  a  strong  pre- 


444  THE  EVOLUTION  OF  LIFE. 

sumption  that  the  groups  within  groups  which  constitute  the 
animal  and  vegetal  kingdoms,  have  arisen  by  direct  descent, 
multiplication,  and  divergence — that  is,  by  evolution. 

§  124.  Strong  confirmation  of  this  inference  is  yielded  by 
the  fact,  that  the  more  marked  differences  which  divide 
groups  are,  in  both  cases,  distinguished  from  the  less  marked 
differences  which  divide  sub-groups,  by  this,  that  they  are 
not  simply  greater  in  degree,  but  they  are  more  radical  in 
kind.  Objects,  as  the  stars,  may  present  themselves  in  small 
clusters,  which  are  again  more  or  less  aggravated  into  clusters 
of  clusters,  in  such  manner  that  the  individuals  of  each 
simple  cluster  are  much  closer  together  than  are  the  simple 
clusters  gathered  into  a  compound  cluster :  in  which  case,  the 
trait  that  unites  groups  of  groups  differs  from  the  trait  that 
unites  groups,  not  in  nature  but  only  in  amount.  But  this  is 
not  so  either  with  the  groups  and  sub-groups  which  we  know 
have  resulted  from  evolution,  or  with  those  which  we  here 
infer  have  resulted  from  evolution.  In  both  cases  the  highest 
or  most  general  classes,  are  marked  off  from  one  another  by 
fundamental  differences  that  have  no  common  measure  with 
the  differences  that  mark  off  small  classes.  Observe  the 
parallelism. 

We  saw  that  each  sub-kingdom  of  animals  is  distinguished 
from  other  sub-kingdoms,  by  some  unlikeness  in  its  main 
plan  of  organization;  such  as  the  presence  or  absence  of  a 
peri-visceral  cavity.  Contrariwise,  the  members  of  the 
smallest  groups  are  united  together,  and  separated  from  the 
members  of  other  small  groups,  by  modifications  which  do 
not  affect  the  relations  of  essential  parts.  That  this  is  just 
the  kind  of  arrangement  which  results  from  evolution,  the 
case  of  languages  will  show. 

On  comparing  the  dialects  spoken  in  different  parts  of 
England,  we  find  scarcely  any  difference  but  those  of  pro- 
nunciation: the  structures  of  the  sentences  are  almost  uni- 
form. Between  English  and  the  allied  modern  languages 


THE  ARGUMENTS  FROM  CLASSIFICATION.          445 

there  are  divergences  of  structure:  there  are  some  unlike- 
nesses  of  idiom ;  some  unlikenesses  in  the  ways  of  modifying 
the  meanings  of  verbs;  and  considerable  unlikenesses  in  the 
uses  of  genders.  But  these  unlikenesses  are  not  sufficient 
to  hide  a  general  community  of  organization.  A  greater  con- 
trast of  structure  exists  between  these  modern  languages  of 
Western  Europe,  and  the  classic  languages.  Differentiation 
into  abstract  and  concrete  elements,  which  is  shown  by  the 
substitution  of  auxiliary  words  for  inflections,  has  produced 
a  higher  specialization,  distinguishing  these  languages  as  a 
group  from  the  older  languages.  Nevertheless,  both  the 
ancient  and  modern  languages  of  Europe,  together  with  some 
Eastern  languages  derived  from  the  same  original,  have, 
under  all  their  differences  of  organization,  a  fundamental  like- 
ness; since  in  all  of  them  words  are  formed  by  such  a  coal- 
escence and  integration  of  roots  as  destroys  the  independent 
meanings  of  the  roots.  These  Aryan  languages,  and  others 
which  have  the  amalgamate  character,  are  united  by  it  into  a 
class  distinguished  from  the  aptotic  and  agglutinate  lan- 
guages; in  which  the  roots  are  either  not  united  at  all,  or  so 
incompletely  united  that  one  of  them  still  retains  its  inde- 
pendent meaning.  And  philologists  find  that  these  radical 
traits  which  severally  determine  the  grammatical  forms,  or 
modes  of  combining  ideas,  characterize  the  primary  divisions 
among  languages. 

So  that  among  languages,  where  we  know  that  evolution 
has  been  going  on,  the  greatest  groups  are  marked  off  from 
one  another  by  the  strongest  structural  contrasts;  and  as  the 
like  holds  among  groups  of  organisms,  there  results  a  further 
reason  for  inferring  that  these  have  been  evolved. 

§  125.  There  is  yet  another  parallelism  of  like  meaning. 
We  saw  (§  101)  that  the  successively-subordinate  groups — 
classes,  orders,  genera,  and  species — into  which  zoologists  and 
botanists  segregate  animals  and  plants,  have  not,  in  reality, 
those  definite  values  conventionally  given  to  them.  There 


446  THE  EVOLUTION  OF  LIFE. 

are  well-marked  species,  and  species  so  imperfectly  marked 
that  some  systematists  regard  them  as  varieties.  Between 
genera  strong  contrasts  exist  in  many  cases,  and  in  other 
cases  contrasts  so  much  less  decided  as  to  leave  it  doubt- 
ful whether  they  imply  generic  distinctions.  So,  too,  is  it 
with  orders  and  classes:  in  some  of  which  there  have  been 
introduced  sub-divisions,  having  no  equivalents  in  others. 
Even  of  the  sub-kingdoms  the  same  truth  holds.  The  con- 
trast between  the  Ccelenterata  and  the  Mollusca,  is  far  less 
than  that  between  the  Ccelenterata  and  the  V ertebrata. 

Now  just  this  same  indefiniteness  of  value,  or  incomplete- 
ness of  equivalence,  is  observable  in  those  simple  and  com- 
pound and  re-compound  groups  which  we  see  arising  by 
evolution.  In  every  case  the  endeavour  to  arrange  the 
divergent  products  of  evolution,  is  met  by  a  difficulty  like 
that  which  would  meet  the  endeavour  to  classify  the  branches 
of  a  tree,  into  branches  of  the  first,  second,  third,  fourth,  &c., 
orders — the  difficulty,  namely,  that  branches  of  intermediate 
degrees  of  composition  exist.  The  illustration  furnished  by 
languages  wilLserve  us  once  more.  Some  dialects  of  English 
are  but  little  contrasted ;  others  are  strongly  contrasted.  The 
alliances  of  the  several  Scandinavian  tongues  with  one  another 
are  different  in  degree.  Dutch  is  much  less  distinct  from 
German  than  Swedish  is;  while  between  Danish  and 
Swedish  there  is  so  close  a  kinship  that  they  might  almost 
be  regarded  as  widely-divergent  dialects.  Similarly  on  com- 
paring the  larger  divisions,  we  see  that  the  various  languages 
of  the  Aryan  stock  have  deviated  from  their  original  to  very 
unlike  distances.  The  general  conclusion  is  manifest.  While 
the  kinds  of  human  speech  fall  into  groups,  and  sub-groups, 
and  sub-sub-groups;  yet  the  groups  are  not  equal  to  one 
another  in  value,  nor  have  the  sub-groups  equal  values,  nor 
the  sub-sub-groups. 

If,  then,  when  classified,  organisms  fall  into  assemblages 
such  that  those  of  the  same  grade  are  but  indefinitely  equiva- 
lent; and  if,  where  evolution  is  known  to  have  tal\en  place, 


THE  ARGUMENTS  FROM  CLASSIFICATION.          447 

there  have  arisen  assemblages  between  which  the  equivalence 
is  similarly  indefinite;  there  is  additional  reason  for  in- 
ferring that  organisms  are  products  of  evolution. 

§  126.  A  fact  of  much  significance  remains.  If  groups  of 
organic  forms  have  arisen  by  divergence  and  re-divergence; 
and  if,  while  the  groups  have  been  developing  from  simple 
groups  into  compound  groups,  each  group  and  sub-group  has 
been  giving  origin  to  more  complex  forms  of  its  own  type; 
then  it  is  inferable  that  there  once  existed  greater  structural 
likenesses  between  the  members  of  allied  groups  than  exists 
now.  This,  speaking  generally,  proves  to  be  so. 

Between  the  sub-kingdoms  the  gaps  are  extremely  wide; 
but  such  distant  kinships  as  may  be  discerned,  bear  out  anti- 
cipation. Thus  in  the  formation  of  the  germinal  layers  there 
is  a  general  agreement  among  them;  and  there  is  a  further 
agreement  among  sundry  of  them  in  the  formation  of  a 
gastrula.  This  simplest  and  earliest  likeness,  significant  of 
primitive  kinship,  is  in  most  cases  soon  obscured  by  divergent 
modes  of  development;  but  sundry  sub-kingdoms  continue 
to  show  relationships  by  the  likenesses  of  their  larval  forms; 
as  we  see  in  the  trochophores  of  the  Polyzoa,  Annelida,  and 
Mollusca — sub-kingdoms  the  members  of  which  by  their  later 
structural  changes  are  rendered  widely  unlike. 

More  decided  approximations  exist  between  the  lower 
members  of  classes.  In  tracing  down  the  Crustacea  and  the 
Arachnida  from  their  more  complex  to  their  simpler  forms, 
zoologists  meet  with  difficulties:  respecting  some  of  these 
simpler  forms,  it  becomes  a  question  which  class  they  belong 
to.  The  Lepidosiren,  about  which  there  have  been  disputes 
whether  it  is  a  fish  or  an  amphibian,  is  inferior,  in  the  organi- 
zation of  its  skeleton,  to  the  great  majority  of  both  fishes  and 
amphibia.  Widely  as  they  differ  from  them,  the  lower  mam- 
mals have  some  characters  in  common  with  birds,  which  the 
higher  mammals  do  not  possess. 

Now  since  this  kind  of  relationship  of  groups  is  not  ac- 


448  THE  EVOLUTION  OP  LIFE. 

counted  for  by  any  other  hypothesis,  while  the  hypothesis  of 
evolution  gives  us  a  clue  to  it;  we  must  include  it  among 
the  supports  of  this  hypothesis  which  the  facts  of  classifica- 
tion furnish. 

§  127.  What  shall  we  say  of  these  leading  truths  when 
taken  together?  That  naturalists  have  been  gradually  com- 
pelled to  arrange  organisms  in  groups  within  groups,  and  that 
this  is  the  arrangement  which  we  see  arises  by  descent,  alike 
in  individual  families  and  among  races  of  men,  is  a  striking 
circumstance.  That  while  the  smallest  groups  are  the  most 
nearly  related,  there  exist  between  the  great  sub-kingdoms, 
structural  contrasts  of  the  profoundest  kind,  cannot  but  im- 
press us  as  remarkable,  when  we  see  that  where  it  is  known  to 
take  place  evolution  actually  produces  these  feebly-distin- 
guished small  groups,  and  these  strongly-distinguished  great 
groups.  The  impression  made  by  these  two  parallelisms,  which 
add  meaning  to  each  other,  is  deepened  by  the  third  parallel- 
ism, which  enforces  the  meaning  of  both — the  parallelism, 
namely,  that  as,  between  the  species,  genera,  orders,  classes, 
&c.,  which  naturalists  have  formed,  there  are  transitional 
types;  so  between  the  groups,  sub-groups,  and  sub-sub-groups, 
which  we  know  to  have  been  evolved,  types  of  intermediate 
values  exist.  And  these  three  correspondences  between  the 
known  results  of  evolution  and  the  results  here  ascribed  to 
evolution,  have  further  weight  given  to  them  by  the  fact,  that 
the  kinship  of  groups  through  their  lowest  members  is  just 
the  kinship  which  the  hypothesis  of  evolution  implies. 

Even  in  the  absence  of  these  specific  agreements,  the  broad 
fact  of  unity  amid  multiformity,  which  organisms  so  strik- 
ingly display,  is  strongly  suggestive  of  evolution.  Freeing 
ourselves  from  pre-conceptions,  we  shall  see  good  reason  to 
think  with  Mr.  Darwin,  "  that  propinquity  of  descent — the 
only  known  cause  of  the  similarity  of  organic  beings — is  the 
bond,  hidden  as  it  is  by  various  degrees  of  modification, 
which  is  partly  revealed  to  us  by  our  classifications."  When 


THE  ARGUMENTS  PROM  CLASSIFICATION.         449 

we  consider  that  this  only  known  cause  of  similarity,  joined 
with  the  only  known  cause  of  divergence  (the  influence  of 
conditions),  gives  us  a  key  to  these  likenesses  obscured  by 
unlikenesses ;  we  shall  see  that  were  there  none  of  those 
remarkable  harmonies  above  pointed  out,  the  truths  of  classi- 
fication would  still  yield  strong  support  to  our  conclusion. 


CHAPTER  V. 

THE    ARGUMENTS    FROM    EMBRYOLOGY. 

§  127a.  ALREADY  I  have  emphasized  the  truth  that  Nature 
is  always  more  complex  than  we  suppose  (§  7-ia) — that  there 
are  complexities  within  complexities.  Here  we  find  illus- 
trated this  truth  under  another  aspect.  When  seeking  to 
formulate  the  arguments  from  Embryology,  we  are  shown 
that  the  facts  as  presented  in  Nature  are  not  to  be  expressed 
in  the  simple  generalizations  we  at  first  make. 

While  we  recognize  this  truth  we  must  also  recognize  the 
truth  that  only  by  enunciation  and  acceptance  of  imperfect 
generalizations  can  we  progress  to  perfect  ones.  The  order 
of  Evolution  is  conformed  to  by  ideas  as  by  other  things.  The 
advance  is,  and  must  be,  from  the  indefinite  to  Jhe  definite. 
It  is  impossible  to  express  the  totality  of  any  natural  pheno- 
menon in  a  single  proposition.  To  the  primary  statement 
expressing  that  which  is  most  dominant  have  to  be  added 
secondary  statements  qualifying  it.  We  see  this  even  in  so 
simple  a  case  as  the  flight  of  a  projectile.  The  young  artillery 
officer  is  first  taught  that  a  cannon-shot  describes  a  curve 
treated  as  a  parabola,  though  literally  part  of  an  extremely 
eccentric  ellipse  not  distinguishable  from  a  parabola.  Pre- 
sently he  learns  that  atmospheric  resistance,  causing  a  con- 
tinual decrease  of  .velocity,  entails  a  deviation  from  that 
theoretical  path  which  is  calculated  on  the  supposition  that 
the  velocity  is  uniform;  and  this  incorrectness  he  has  to 
450 


THE  ARGUMENTS  FROM  EMBRYOLOGY.  451 

allow  for.  Then,  further,  there  comes  the  lateral  deviation 
due  to  wind,  which  may  be  appreciable  if  the  wind  is  strong 
and  the  range  great.  To  introduce  him  all  at  once  to  the 
correct  conception  thus  finally  reached  would  be  impossible: 
it  has  to  be  reached  through  successive  qualifications.  And 
that  which  holds  even  in  this  simple  case  necessarily  holds 
more  conspicuously  in  complex  cases. 

The  title  of  the  chapter  suggests  a  metdphor,  which  is, 
indeed,  something  more  than  a  metaphor.  There  is  an  em- 
bryology of  conceptions.  That  this  statement  is  not  wholly 
a  figure  of  speech,  we  shall  see  on  considering  that  cerebral 
organization  is  a  part  of  organization  at  large;  and  that  the 
evolving  nervous  plexus  which  is  the  correlative  of  an  evolv- 
ing conception,  must  conform  to  the  general  law  of  change 
conformed  to  in  the  evolution  of  the  whole  nervous  structure 
as  well  as  in  the  evolution  of  the  whole  bodily  structure.  As 
the  body  has  at  first  a  rude  form,  very  remotely  suggesting 
that  which  is  presently  developed  by  the  superposing  of  modi- 
fications on  modifications ;  so  the  brain  as  a  whole  and  its  con- 
tained ideas  together  make  up  an  inner  world  answering  with 
extreme  indefiniteness  to  that  outer  world  to  which  it  is 
brought  by  successive  approximations  into  tolerable  corre- 
spondence ;  and  so  any  nervous  plexus  and  its  associated  hypo- 
thesis, which  refer  to  some  external  group  of  phenomena  under 
investigation,  have  to  reach  their  final  developments  by 
successive  corrections. 

This  being  the  course  of  discovery  must  also  be  the  course 
of  exposition.  In  pursuance  of  this  course  we  may  there- 
fore fitly  contemplate  that  early  formula  of  embryological 
development  which  we  owe  to  von  Baer. 

§  128.  Already  in  §  52,  where  the  generalization  of  von 
Baer  respecting  the  relations  of  embryos  was  set  forth,  there 
was  given  the  warning,  above  repeated  with  greater  distinct- 
ness, that  it  is  only  an  adumbration. 

In  the  words  of  his  translator,  he  "found  that  in  its  earliest 


452  THE  EVOLUTION  OP  LIFE. 

stage,  every  organism  has  the  greatest  number  of  characters 
in  common  with  all  other  organisms  in  their  earliest  stages; 
that  at  a  stage  somewhat  later,  its  structure  is  like  the  struc- 
tures displayed  at  corresponding  phases  by  a  less  extensive 
multitude  of  organisms;  that  at  each  subsequent  stage, 
traits  are  acquired  which  successively  distinguished  the  de- 
veloping embryo  from  groups  of  embryos  that  it  previously 
resembled — thus  step  by  step  diminishing  the  class  of 
embryos  which  it  still  resembles;  and  that  thus  the  class  of 
similar  forms  is  finally  narrowed  to  the  species  of  which  it  is 
a  member." 

Assuming  for  a  moment  that  this  generalization  is  true  as 
it  stands,  or  rather,  assuming  that  the  qualifications  needed 
are  not  such  as  destroy  its  correspondence  with  the  average 
facts,  we  shall  see  that  it  has  profound  significance.  For  if 
we  follow  out  in  thought  the  implications — if  we  conceive 
the  germs  of  all  kinds  of  organisms  simultaneously  develop- 
ing, and  imagine  that  after  taking  their  first  step  together, 
at  the  second  step  one  half  of  the  vast  multitude  diverges 
from  the  other  half;  if,  at  the  next  step,  we  mentally  watch 
the  parts  of  each  great  assemblage  beginning  to  take  two  or 
more  routes  of  development;  if  we  represent  to  ourselves 
such  bifurcations  going  on,  stage  after  stage,  in  all  the 
branches;  we  shall  see  that  there  must  result  an  aggregate 
analogous,  in  its  arrangement  of  parts,  to  a  tree.  If  this  vast 
genealogical  tree  be  contemplated  as  a  whole,  made  up  of 
trunk,  main  branches,  secondary  branches,  and  so  on  as  far 
as  the  terminal  twigs;  it  will  be  perceived  that  all  the 
various  kinds  of  organisms  represented  by  these  terminal 
twigs,  forming  the  periphery  of  the  tree,  will  stand  related 
to  one  another  in  small  groups,  which  are  united  into  groups 
of  groups,  and  so  on.  The  embryological  tree,  expressing  the 
developmental  relations  of  organisms,  will  be  similar  to  the 
tree  which  symbolizes  their  classificatory  relations.  That 
subordination  of  classes,  orders,  genera,  and  species,  to  which 
naturalists  have  been  gradually  led,  is  just  that  subordination 


THE  ARGUMENTS  FROM  EMBRYOLOGY.     453 

which  results  from  the  divergence  and  re-divergence  of 
embryos,  as  they  all  unfold.  On  the  hypothesis  of  evolution 
this  parallelism  has  a  meaning — indicates  that  primordial 
kinship  of  all  organisms,  and  that  progressive  differentiation 
of  them,  which  the  hypothesis  alleges.  But  on  any  other 
hypothesis  the  parallelism  is  meaningless;  or  rather,  it  raises 
a  difficulty;  since  it  implies  either  an  effect  without  a  cause 
or  a  design  without  a  purpose. 

§  129.  This  conception  of  a  tree,  symbolizing  the  relation- 
ships of  types  and  a  species  derived  from  the  same  root,  has 
a  concomitant  conception.  The  implication  is  that  each 
organism,  setting  out  from  the  simple  nucleated  cell,  must  in 
the  course  of  its  development  follow  the  line  of  the  trunk, 
some  main  branch,  some  sub-branch,  some  sub-sub-branch, 
&c.,  of  this  embryological  tree;  and  so  on  till  it  reaches  that 
ultimate  twig  representing  the  species  of  which  it  is  a  member. 
It  must  in  a  general  way  go  through  the  particular  line  of 
forms  which  preceded  it  in  all  past  times:  there  must  be 
what  has  been  aptly  called  a  "recapitulation"  of  the  suc- 
cessive ancestral  structures.  This,  at  least,  is  the  conclusion 
necessitated  by  the  generalization  we  are  considering  under 
its  original  crude  form. 

Yon  Baer  lived  in  the  days  when  the  Development  Hypo- 
thesis was  mentioned  only  to'  be  ridiculed,  and  he  joined 
in  the  ridicule.  What  he  conceived  to  be  the  meaning  of 
these  groupings  of  organisms  and  these  relations  among  their 
embryological  histories,  is  not  obvious.  The  only  alternative 
to  the  hypothesis  of  Evolution  is  the  hypothesis  of  Special 
Creation ;  and  as  he  did  not  accept  the  one  it  is  inferable  that 
he  accepted  the  other.  But  if  he  did  this  he  must  in  the 
first  place  have  found  no  answer  to  the  inquiry  why  organisms 
specially  created  should  have  the  embryological  kinships  he 
described.  And  in  the  second  place,  after  discovering  that 
his  alleged  law  was  traversed  by  many  and  various  noncon- 
formities, he  would  have  been  without  any  explanation  of 


454  THE  EVOLUTION  OF  LIFE. 

these.  Observe  the  positions  which  were  open  to  him  and 
the  reasons  which  show  them  to  be  untenable. 

If  it  be  said  that  the  conditions  of  the  case  necessitated 
the  derivation  of  all  organisms  from  simple  germs,  and  there- 
fore necessitated  a  morphological  unity  in  their  primitive 
states ;  there  arises  the  obvious  answer,  that  the  morphologi- 
cal unity  thus  implied,  is  not  the  only  morphological  unity 
to  be  accounted  for.  Were  this  the  only  unity,  the  various 
kinds  of  organisms,  setting  out  from  a  common  primordial 
form,  should  all  begin  from  the  first  to  diverge  individually, 
as  so  many  radii  from  a  centre;  which  they  do  not.  If,  other- 
wise, it  be  said  that  organisms  were  framed  upon  certain 
types,  and  that  those  of  the  same  type  continue  developing 
together  in  the  same  direction,  until  it  is  time  for  them  to 
begin  putting  on  their  specialities  of  structure;  then  the 
answer  is,  that  when  they  do  finally  diverge  they  ought 
severally  to  develop  in  direct  lines  towards  their  final  forms. 
No  reason  can  be  assigned  why,  having  parted  company,  some 
should  progress  towards  their  final  forms  by  irregular  or  cir- 
cuitous routes.  On  the  hypothesis  of  design  such  deviations 
are  inexplicable. 

The  hypothesis  of  evolution,  however,  while  it  pre-supposes 
those  kinships  among  embryos  in  their  early  forms  which 
are  found  to  exist,  also  leads  us  to  expect  nonconformities  in 
their  courses  of  development.  If,  as  any  rational  theory  of 
evolution  implies,  the  progressive  differentiations  of  types 
from  one  another  during  past  times,  have  resulted  from 
thf  direct  and  indirect  effects  of  external  conditions — if 
races  of  organisms  have  become  different,  either  by  imme- 
diate adaptations  to  unlike  habits  of  life,  or  by  the  mediate 
adaptations  resulting  from  preservation  of  the  individuals 
most  fitted  for  such  habits  of  life,  or  by  both;  and  if 
most  embryonic  changes  are  significant  of  changes  that 
were  undergone  by  ancestral  races;  then  these  irregularities 
must  be  anticipated.  For  the  successive  changes  in  modes  of 
life  pursued  by  successive  ancestral  races,  can  have  had  no 


THE  ARGUMENTS  FROM  EMBRYOLOGY.  455 

regularity  of  sequence.  In  some  cases  they  must  have  been 
more  numerous  than  in  others;  in  some  cases  they  must 
have  been  greater  in  degree  than  in  others;  in  some  cases 
they  must  have  been  to  simpler  modes,  in  some  cases  to 
more  complex  modes,  and  in  some  cases  to  modes  neither 
higher  nor  lower.  Of  two  cognate  races  which  diverged  in 
the  remote  past,  the  one  may  have  had  descendants  that 
have  remained  tolerably  constant  in  their  habits,  while  the 
other  may  have  had  descendants  that  have  passed  through 
widely-aberrant  modes  of  life;  and  yet  some  of  these  last 
may  have  eventually  taken  to  modes  of  life  like  those  of  the 
other  races  derived  from  the  same  stock.  And  if  the  meta- 
morphoses of  embryos  indicate,  in  a  general  way,  the  changes 
of  structure  undergone  by  ancestors;  then,  the  later  embryo- 
logic  changes  of  such  two  allied  races  will  be  somewhat 
different,  though  they  may  end  in  very  similar  forms.  An 
illustration  will  make  this  clear.  Mr.  Darwin  says: 
"  Petrels  are  the  most  aerial  and  oceanic  of  birds,  but  in  the 
quiet  sounds  of  Tierra  del  Fuego,  the  Puffinuria  berardi,  in 
its  general  habits,  in  its  astonishing  power  of  diving,  its 
manner  of  swimming,  and  of  flying  when  unwillingly  it  takes 
flight,  would  be  mistaken  by  any  one  for  an  auk  or  grebe; 
nevertheless,  it  is  essentially  a  petrel,  but  with  many  parts  of 
its  organization  profoundly  modified."  Now  if  we  suppose 
these  grebe-like  habits  to  be  continued  through  a  long  epoch, 
the  petrel-form  to  be  still  more  obscured,  and  the  approxi- 
mation to  the  grebe- form  still  closer;  it  is  manifest  that 
while  the  chicks  of  the  grebe  and  the  Puffinuria  will,  during 
their  early  stages  of  development,  display  that  likeness  in- 
volved by  their  common  derivation  from  some  early  type  of 
bird,  the  chick  of  the  Puffinuria  will  eventually  begin  to 
show  deviations,  representative  of  the  ancestral  petrel-struc- 
ture, and  will  afterwards  begin  to  lose  these  distinctions  and 
assume  the  grebe-structure. 

Hence,  remembering  the  perpetual  intrusions  of  organisms 
on  one  another's  modes  of  life,  often  widely  different;    and 


456  'THE  EVOLUTION  OF  LIFE. 

remembering  that  these  intrusions  have  been  going  on  from 
the  beginning;  we  shall  be  prepared  to  find  that  the  general 
law  of  embryonic  parallelism  is  qualified  by  irregularities 
which  are  mostly  small,  in  many  cases  considerable,  and  occa- 
sionally great.  The  hypothesis  of  evolution  accounts  for 
these :  it  does  more — it  implies  the  necessity  of  them. 

§  130.  The  substitutions  of  organs  and  the  suppressions  of 
organs,  are  among  those  secondary  embryological  phenomena 
which  harmonize  with  the  belief  in  evolution  but  cannot  be 
reconciled  with  any  other  belief.  Some  embryos,  during 
early  stages  of  development,  possess  organs  that  afterwards 
dwindle  away,  as  there  arise  other  organs  to  discharge  the 
same  functions.  And  in  other  embryos  organs  make  their 
appearance,  grow  to  certain  points,  have  no  functions  to  dis- 
charge, and  disappear  by  absorption. 

We  have  a  remarkable  instance  of  substitution  in  the 
temporary  appliances  for  respiration,  which  some  embryos 
exhibit.  During  the  first  phase  of  its  development,  the  mam- 
malian embryo  possesses  a  system  of  blood-vessels  distributed 
over  what  is  called  the  area  vasculosa — a  system  of  vessels 
homologous  with  one  which,  among  fishes,  serves  for  aerating 
the  blood  until  the  permanent  respiratory  organs  come  into 
play.  Now  since  this  system  of  blood-vessels,  not  being  in 
proximity  to  an  oxygenated  medium,  cannot  be  serviceable 
to  the  mammalian  embryo  during  development  of  the  lungs, 
as  it  is  serviceable  in  the  embryo-fish  during  development  of 
the  gills,  this  needless  formation  of  it  is  unaccountable  as 
a  result  of  design.  But  it  is  quite  congruous  with  the  sup- 
position that  the  mammalian  type  arose  out  of  lower  verte- 
brate types.  For  in  such  case  the  mammalian  embryo,  pass- 
ing through  states  representing  in  a  general  way  those  which 
its  remote  ancestors  had  in  common  with  the  lower  Verte- 
brata,  develops  this  system  of  vessels  in  like  manner'  with 
them.  An  instance  more  significant  still  is  furnished 

by  certain  Amphibia.  One  of  the  facts  early  made  familiar 


THE  ARGUMENTS  FROM   EMBRYOLOGY.  457 

to  the  natural-history  student  is  that  the  tadpole  breathes 
by  external  branchiag,  and  that  these,  needful  during  its 
aquatic  life,  dwindle  away  as  fast  as  it  develops  the  lungs 
fitting  it  for  terrestrial  life.  But  in  one  of  the  higher 
Amphibia,  the  viviparous  Salamander,  these  transformations 
ordinarily  undergone  during  the  free  life  of  the  larva,  are 
undergone  by  the  embryo  in  the  egg.  The  branchiae  are 
developed  though  there  is  no  use  for  them :  lungs  being  sub- 
stituted as  breathing  appliances  before  the  creature  is  born. 

Even  more  striking  than  the  substitutions  of  organs  are 
the  suppressions  of  organs.  Mr.  Darwin  names  some  cases 
as  "  extremely  curious ;  for  instance,  the  presence  of  teeth  in 
foetal  whales,  which  when  grown  up  have  not  a  tooth  in  their 
heads;  ...  It  has  even  been  stated  on  good  authority  that 
rudiments  of  teeth  can  be  detected  in  the  beaks  of  certain 
embryonic  birds."  Irreconcilable  with  any  teleological  theory, 
these  facts  do  not  even  harmonize  with  the  theory  of  fixed 
types  which  are  maintained  by  the  development  of  all  the 
typical  parts,  even  where  not  wanted;  seeing  that  the  dis- 
appearance of  these  incipient  organs  during  foetal  life  spoils 
the  typical  resemblance.  But  while  to  other  hypotheses  these 
facts  arc  stumbling-blocks,  they  yield  strong  support  to  the 
hypothesis  of  evolution. 

Allied  to  these  cases,  are  the  cases  of  what  has  been  called 
retrograde  development.  Many  parasitic  creatures  and 
creatures  which,  after  leading  active  lives  for  a  time,  become 
fixed,  lose,  in  their  adult  states,  the  limbs  and  senses  they 
had  when  young.  It  may  be  alleged,  however,  that  these 
creatures  could  not  secure  the  habitats  needful  for  them, 
without  possessing,  during  their  larval  stages,  eyes  and  swim- 
ming appendages  which  eventually  become  useless;  that 
though,  by  losing  these,  their  organization  retrogresses  in  one 
direction,  it  progresses  in  another  direction;  and  that,  there- 
fore, they  do  not  exhibit  the  needless  development  of  a 
higher  type  on  the  way  to  a  lower  type.  Nevertheless  there 
are  instances  of  a  descent  in  organization,  following  an  appa- 


458  THE  EVOLUTION  OF  LIFE. 

rently-superfluous  ascent.  Mr.  Darwin  says  that  in  some 
genera  of  cirripedes,  "  the  Iarva3  become  developed  either 
into  hermaphrodites  haying  the  ordinary  structure,  or  into 
what  I  have  called  complemental  males,  and  in  the  latter, 
the  development  has  assuredly  been  retrograde;  for  the  male 
is  a  mere  sack,  which  lives  for  a  short  time,  and  is  destitute 
of  mouth,  stomach,  or  other  organ  of  importance,  excepting 
for  reproduction." 

§  130a.  But  now  let  us  contemplate  more  closely  the 
energies  at  work  in  the  unfolding  embryo,  or  rather  the 
energies  which  the  facts  appear  to  imply. 

Whatever  natures  we  ascribe  to  the  hypothetical  units 
proper  to  each  kind  of  organism,  we  must  conclude  that  from 
the  beginning  of  embryonic  development,  they  have  a  pro- 
clivity towards  the  structure  of  that  organism.  Because  of 
their  phylogenetic  origin,  they  must  tend  towards  the  form  of 
the  primitive  type;  but  the  superposed  modifications,  con- 
flicting with  their  initial  tendency,  must  cause  a  swerving 
towards  each  successively  higher  type.  To  take  an  illustra- 
tion:— If  in  the  germ-plasm  out  of  which  will  come  a  verte- 
brate animal  there  is  a  proclivity  towards  the  primitive 
piscine  form,  there  must,  if  the  germ-plasm  is  derived  from  a 
mammal,  be  also  from  the  outset  a  proclivity  towards  the 
mammalian  form.  While  the  initial  type  tends  continually 
to  establish  itself  the  terminal  type  tends  also  to  establish 
itself.  The  intermediate  structures  must  be  influenced  by 
their  conflict,  as  well  as  by  the  conflict  of  each  with  the  pro- 
clivities towards  the  amphibian  and  reptilian  types.  This 
complication  of  tendencies  is  increased  by  the  intervention  of 
several  other  factors. 

There  is  the  factor  of  economy.  An  embryo  in  which  the 
transformations  have  absorbed  the  smallest  amount  of  energy 
and  wasted  the  smallest  amount  of  matter,  will  have  an 
advantage  over  embryos  the  transformations  of  which  have 
cost  more  in  energy  and  matter:  the  young  animal  will  set 


THE  ARGUMENTS  FROM   EMBRYOLOGY.  459 

out  with  a  greater  surplus  of  vitality,  and  will  be  more  likely 
than  others  to  live  and  propagate.  Again,  in  the  embryos  of 
its  descendants,  inheriting  the  tendency  to  economical  trans- 
formation, those  which  evolve  at  the  least  cost  will  thrive 
more  than  the  rest  and  be  more  likely  to  have  posterity. 
Thus  will  result  a  continual  shortening  of  the  processes.  We 
can  see  alike  that  this  must  take  place  and  that  it  does  take 
place.  If  the  whole  series  of  phylogenetic  changes  had  to  be 
repeated — if  the  embryo  mammal  had  to  become  a  complete 
fish,  and  then  a  complete  amphibian,  and  then  a  complete 
reptile,  there  would  be  an  immense  amount  of  superfluous 
building  up  and  pulling  down,  entailing  great  waste  of  time 
and  of  materials.  Evidently  these  abridgments  which  econo- 
my entails,  necessitate  that  unfolding  embryos  bear  but  rude 
resemblances  to  lower  types  ancestrally  passed  through — 
vaguely  represent  their  dominant  traits  only. 

From  this  principle  of  economy  arise  several  derivative 
principles,  which  may  be  best  dealt  with  separately. 

§  130&.  In  some  cases  the  substitution  of  an  abridged  for 
an  unabridged  course  of  evolution  causes  the  entire  disappear- 
ance of  certain  intermediate  forms.  Structural  arrangements 
once  passed  through  during  the  unfolding  are  dropped  out  of 
the  series. 

In  the  evolution  of  these  embryos  with  which  there  is  not 
laid  up  a  large  amount  of  food-yolk  there  occurs  at  the  outset 
a  striking  omission  of  this  kind.  When,  by  successive 
fissions,  the  fertilized  cell  has  given  rise  to  a  cluster  of  cells 
constituting  a  hollow  sphere,  known  as  a  Uastula,  the  next 
change  under  its  original  form  is  the  introversion  of  one  side, 
so  as  to  produce  two  layers  in  place  of  one.  An  idea  of  the 
change  may  be  obtained  by  taking  an  india-rubber  ball  (hav- 
ing a  hole  through  which  the  air  may  escape)  and  thrusting  in 
one  side  until  its  anterior  surface  touches  the  interior  surface 
of  the  other  side.  If  the  cup-shaped  structure  resulting  be 
supposed  to  have  its  wide  opening  gradually  narrowed,  until  it 


460  THE  EVOLUTION  OP  LIFE. 

becomes  the  mouth  of  an  internal  chamber,  it  will  represent 
what  is  known  as  a  gastrula — a  double  layer  of  cells,  of  which 
the  outer  is  called  epiblast  and  the  inner  hypoblast  (answering 
to  ectoderm  and  endoderm)  inclosing  a  cavity  known  as  the 
archenteron,  or  primitive  digestive  sac.  But  now  in  place  of 
this  original  mode  of  forming  the  gastrula,  there  occurs  a 
mode  known  as  delamination.  Throughout  its  whole  extent 
the  single  layer  splits  so  as  to  become  a  double  layer — one 
sphere  of  cells  inclosing  the  other;  and  after  this  direct  for- 
mation of  the  double  layer  there  is  a  direct  formation  of 
an  opening  through  it  into  the  internal  cavity.  There  is  thus 
a  shortening  of  the  primitive  process:  a  number  of  changes 
are  left  out. 

Often  a  kindred  passing  over  of  stages  at  later  periods 
of  development  may  be  observed.  In  certain  of  the  Mollusca, 
as  the  Patella  chiton,  the  egg  gives  origin  to  a  free-swimming 
larva  known  as  a  trochosphere,  from  which  presently  comes 
the  ordinary  molluscous  organization.  In  the  highest  division 
of  the  Molluscs,  however,  the  Cephalopods,  no  trochosphere  is 
formed.  The  nutritive  matter  laid  up  in  the  egg  is  used 
in  building  up  the  young  animal  without  any  indication  of  an 
ancestral  larva. 

§  130c.  Among  principles  derived  from  the  principle  of 
economy  is  the  principle  of  pre-adaptation — a  name  which  we 
may  appropriately  coin  to  indicate  an  adaptation  made  in 
advance  of  the  time  at  which  it  could  have  arisen  in  the 
course  of  phylogenetic  history. 

How  pre-adaptation  may  result  from  economy  will  be 
shown  by  an  illustration  which  human  methods  of  con- 
struction furnish.  Let  us  assume  that  building  houses  of 
a  certain  type  has  become  an  established  habit,  and  that, 
as  a  part  of  each  house,  there  is  a  staircase  of  given  size.  And 
suppose  that  in  consequence  of  changed  conditions — say  the 
walling  in  of  the  town,  limiting  the  internal  space  and  in- 
creasing ground-rents — it  becomes  the  policy  to  build  houses 


THE  ARGUMENTS  PROM   EMBRYOLOGY.  461 

of  many  stories,  let  out  in  flats  to  different  tenants.  For  the 
increased  passing  up  and  down,  a  staircase  wider  at  its  lower 
part  will  be  required.  If  now  the  builder,  when  putting  up 
the  ground  floor,  follows  the  old  dimensions,  then  after  all  the 
stories  are  built,  the  lower  part  of  the  staircase,  if  it  is  to 
yield  equal  facilities  for  passage,  must  be  reconstructed. 
Instead  of  a  staircase  adapted  to  those  few  stories  which  the 
original  type  of  house  had,  economy  will  dictate  a  pre-adapta- 
tion  of  the  staircase  to  the  additional  stories. 

On  carrying  this  idea  with  us,  we  shall  see  that  if  from 
some  type  of  organism  there  is  evolved  a  type  in  which 
enlargement  of  a  certain  part  is  needed  to  meet  increased 
functions,  the  greater  size  of  this  part  will  begin  to  show 
itself  during  early  stages  of  unfolding.  That  unbuilding  and 
rebuilding  which  would  be  needful  were  it  laid  down  of  its 
original  size,  will  be  made  needless  if  from  the  beginning 
it  is  laid  down  of  a  larger  size.  Hence,  in  successive  genera- 
tions, the  greater  prosperity  and  multiplication  of  individuals 
in  which  this  part  is  at  the  outset  somewhat  larger  than 
usual,  must  eventually  establish  a  marked  excess  in  its 
development  at  an  early  stage.  The  facts  agree  with  this 
inference. 

Referring  to  the  contrasts  between  embryos,  Mr.  Adam 
Sedgwick  says  that  "  a  species  is  distinct  and  distinguishable 
from  its  allies  from  the  very  earliest  stages."  Whereas, 
according  to  the  law  of  von  Baer,  "  animals  so  closely  allied  as 
the  fowl  and  duck  would  be  indistinguishable  in  the  early 
stages  of  development,"  "yet  I  can  distinguish  a  fowl  and 
a  duck  embryo  on  the  second  day  by  the  inspection  of  a  single 
transverse  section  through  the  trunk."  This  experience 
harmonizes  with  the  statement  of  the  late  Prof.  Agassiz,  that 
in  some  cases  traits  characterizing  the  species  appear  at  an 
earlier  period  than  traits  characterizing  the  genus. 

Similar  in  their  implications  are  the  facts  recently  pub- 
lished by  Dr.  E.  Mehnert,  concerning  the  feet  of  pentadactyle 
vertebrates.  A  leading  example  is  furnished  by  the  foot  in 


462  THE  EVOLUTION   OF   LIFE. 

the  struthious  birds.  Out  of  the  original  five  digits  the  two 
which  eventually  become  large  while  the  others  disappear, 
soon  give  sign  of  their  future  predominance :  their  early  sizes 
being  in  excess  of  those  required  for  the  usual  functional  re- 
quirements in  birds,  and  preparing  the  way  for  their  special 
requirements  in  the  struthious  birds.  Dr.  Mehnert  shows 
that  a  like  lesson  is  given  by  the  relative  developments  of 
legs  and  wings  in  these  birds.  Ordinarily  in  vertebrates  the 
fore  limbs  grow  more  rapidly  than  the  hind  limbs ;  but  in  the 
ostrich,  in  which  the  hind  limbs  or  legs  have  to  become  so 
large  while  the  wings  are  but  little  wanted,  the  leg  develop- 
ment goes  in  advance  of  the  wing-development  in  early 
embryonic  stages:  there  is  a  pre-adaptation. 

Much  more  striking  are  examples  furnished  by  creatures 
whose  modes  of  existence  require  that  they  shall  have 
enormous  fertility — require  that  the  generative  system  shall 
be  very  large.  Ordinarily  the  organs  devoted  to  maintenance 
of  the  race  develop  later  than  the  organs  devoted  to  main- 
tenance of  the  individual.  But  this  order  is  inverted  in 
certain  Entozoa.  To  these  creatures,  imbedded  in  nutritive 
matters,  self-maintenance  cost  nothing,  and  the  structures 
devoted  to  it  are  relatively  of  less  importance  than  the  struc- 
tures devoted  to  race-maintenance,  which,  to  make  up  for  the 
small  chance  any  one  germ  has  of  getting  into  a  fit  habitat, 
have  to  produce  immense  numbers  of  germs.  Here  the  rudi- 
ments of  the  generative  systems  are  the  first  to  become  visible 
— here,  in  virtue  of  the  principle  of  pre-adaptation,  a  struc- 
ture belonging  to  the  terminal  form  asserts  itself  so  early 
in  the  developmental  process  as  almost  to  obliterate  the  struc- 
ture of  the  initial  form. 

It  may  be  that  in  some  cases  where  the  growth  of  certain 
organs  goes  in  advance  of  the  normal  order,  the  element 
of  time  comes  into  play — the  greater  time  required  for  con- 
struction. To  elucidate  this  let  us  revert  to  our  simile. 
Suppose  that  the  staircase  above  instanced,  or  at  any  rate  its 
lower  part,  is  required  to  be  of  marble  with  balusters  finely 


THE  ARGUMENTS  FROM   EMBRYOLOGY.  463 

carved.  If  this  piece  of  work  is  not  promptly  commenced 
and  pushed  on  fast,  it  will  not  be  completed  when  the  rest  of 
the  house  is  ready:  workmen  and  tools  will  still  block  it  up 
at  a  time  when  it  should  be  available.  Similarly  among  the 
parts  of  an  unfolding  embryo,  those  in  which  there  is  a  great 
deal  of  constructive  work  must  early  take  such  shape  as  will 
allow  of  this.  Now  of  all  the  tissues  the  nervous  tissue  is 
that  which  takes  longest  to  repair  when  injured;  and  it 
seems  a  not  improbable  inference  that  it  is  a  tissue  which  is 
slower  in  its  histological  development  than  others.  If  this  be 
so,  we  may  see  why,  in  the  embryos  of  the  higher  vertebrates, 
the  central  nervous  system  quickly  grows  large  in  comparison 
to  the  other  systems — why  by  pre-adaptation  the  brain  of  a 
chick  develops  in  advance  of  other  organs  so  much  more  than 
the  brain  of  a  fish. 

§  I30d.  Yet  another  complication  has  to  be  noted.  From 
the  principle  of  economy,  it  seems  inferable  that  decrease  and 
disappearance  of  organs  which  were  useful  in  ancestral  types 
but  have  ceased  to  be  useful,  should  take  place  uniformly; 
but  they  do  not.  In  the  words  of  Mr.  Adam  Sedgwick, 
"  some  ancestral  organs  persist  in  the  embryo  in  a  function- 
less  rudimentary  (vestigial)  condition  and  at  the  same  time 
without  any  reference  to  adult  structures,  while  other  an- 
cestral organs  have  disappeared  without  leaving  a  trace."  * 
This  anomaly  is  rendered  more  striking  when  joined  with 
the  fact  that  some  of  the  structures  which  remain  con- 
spicuous are  relatively  ancient,  while  some  which  have  been 
obliterated  are  relatively  modern — e.g.,  "gill  slits  [which  date 
back  to  the  fish-ancestor],  have  been  retained  in  embryology, 
whereas  other  organs  which  have  much  more  recently  disap- 
peared, e.  g.  teeth  of  birds,  fore-limbs  of  snakes  [dating  back 
to  the  reptile  ancestor] ,  have  been  entirely  lost."  f  Mr.  Sedg- 
wick ascribes  these  anomalies  to  the  difference  between  larval 

*  Studies  from  (he  Morphological  Laboratory  in  the  University  of  Cam- 
bridge, vol.  vi,  p.  84.  f  #«*i  P-  81. 


404  THE  EVOLUTION  OF  LIFE. 

development  and  embryonic  development,  and  expresses  his 
general  belief  thus : — 

"The  conclusion  here  reached  is  that,  whereas  larval  development 
must  retain  traces  (it  may  be  very  faint)  of  ancestral  stages  of  struc- 
ture because  they  are  built  out  of  ancestral  stages,  embryonic  develop- 
ment need  not  necessarily  do  so,  and  very  often  does  not;  that 
embryonic  development  in  so  far  as  it  is  a  record  at  all,  is  a  record  of 
structural  features  of  previous  larval  stages.  Characters  which  dis- 
appear during  free  life  disappear  also  in  the  embryo,  but  characters 
which  though  lost  by  the  adult  are  retained-  in  the  larva  may  ulti- 
mately be  absorbed  into  the  embryonic  phase  and  leave  their  traces  in 
embryonic  development."  * 

To  set  forth  the  evidence  justifying  this  view  would  en- 
cumber too  much  the  general  argument.  Towards  elucidation 
of  such  irregularities  let  me  name  two  factors  which  should  I 
think  he  taken  into  account. 

Abridgment  of  embryonic  stages  cannot  go  on  uniformly 
with  all  disused  organs.  Where  an  organ  is  of  such  size  that 
progressive  diminution  of  it  will  appreciably  profit  the  young 
animal,  by  leaving  it  a  larger  surplus  of  unused  material,  we 
may  expect  progressive  diminution  to  occur.  Contrariwise, 
if  the  organ  is  relatively  so  small  that  each  decrease  will  not, 
by  sensibly  increasing  the  reserve  of  nutriment,  give  the 
young  animal  an  advantage  over  others,  decrease  must  not  be 
looked  for:  there  may  be  a  survival  of  it  even  though  of 
very  ancient  origin. 

Again,  the  reduction  of  a  superfluous  part  can  take  place 
only  on  condition  that  the  economy  resulting  from  each  de- 
scending variation  of  it,  is  of  greater  importance  than  are 
the  effects  of  variations  simultaneously  occurring  in  other 
parts.  If  by  increase  or  decrease  of  any  other  parts  of  the 
embryo,  survival  of  the  animal  is  furthered  in  a  greater 
degree  than  by  decrease  of  this  superfluous  part,  then  such 
decrease  is  unlikely;  since  it  is  illegitimate  to  count  upon 
the  repeated  concurrence  of  favourable  variations  in  two  or 
more  parts  which  are  independent.  So  that  if  changes  of  an 

*  R'vdi"K  from  the  Morphological  Laboratory  in  the  University  of  Cam- 
bridge, vol.  vi,  p.  89. 


THE  ARGUMENTS  FROM  EMBRYOLOGY.  465 

advantageous  kind  are  going  on  elsewhere  in  the  embryo  a 
useless  part  may  remain  long  undiminished. 

Yet  another  cause  operates,  and  perhaps  cooperates.  Em- 
bryonic survival  of  an  organ  which  has  become  functionless, 
may  readily  happen  if,  during  subsequent  stages  of  develop- 
ment, parts  of  it  are  utilized  as  parts  of  other  organs.  In  the 
words  of  Mr.  J.  T.  Cunningham : — 

"It  seems  to  be  a  general  fact  that  a  structure  which  in  meta- 
morphosis disappears  completely  may  easily  be  omitted  altogether  in 
embryonic  development,  while  one  which  is  modified  into  something 
else  continues  to  pass  more  or  less  through  its  original  larval  condi- 
tion." (Science  Progress,  July,  1897,  p.  488.) 

One  more  factor  of  considerable  importance  should  be 
taken  into  account.  A  disused  organ  which  entails  evil 
because  construction  of  it  involves  needless  cost,  may  entail 
further  evil  by  being  in  the  way.  This,  it  seems  to  me,  is 
the  reason  why  the  fore-limbs  of  snakes  have  disappeared  from 
their  embryos.  When  the  long-bodied  lizard  out  of  which 
the  ophidian  type  evolved,  crept  through  stiff  herbage,  and 
moved  its  head  from  side  to  side  to  find  openings,  there  re- 
sulted alternate  bends  of  its  body,  which  were  the  beginnings 
of  lateral  undulations ;  and  we  may  easily  see  that  in  propor- 
tion as  it  thus  progressed  by  insinuating  itself  through  inter- 
stices, the  fore-limbs,  less  and  less  used  for  walking,  would 
be  more  and  more  in  the  way;  and  the  lengthening  of  the 
body,  increasing  the  undulatory  motion  and  decreasing  the 
use  of  the  fore-limbs,  would  eventually  make  them  absolute 
impediments.  Hence  besides  the  benefit  in  economy  of  con- 
struction gained  by  embryos  in  which  the  fore-limbs  were  in 
early  stages  a  little  less  developed  than  usual,  they  would 
gain  an  advantage  by  having,  when  mature,  smaller  fore- 
limbs  than  usual,  leading  to  greater  facility  of  locomotion. 
There  would  be  a  double  set  of  influences  causing,  through 
selection,  a  comparatively  rapid  decrease  of  these  appendages. 
And  we  may  I  think  see  also,  on  contemplating  the  kind  of 
movement,  that  the  fore-limbs  wo.uld  be  more  in  the  wiy 
than  the  hind  limbs,  which  would  consequently  dwindle  with 


466  THE  EVOLUTION  OP  LIFE. 

such  smaller  rapidity  as  to  make  continuance  of  the  rudi- 
ments of  them  comprehensible. 

§  131—132.  So  that  while  the  embryonic  law  enunciated 
by  von  Baer  is  in  harmony  with  the  hypothesis  of  evolu- 
tion, and  is,  indeed,  a  law  which  this  hypothesis  implies,  the 
nonconformities  to  the  law  are  also  interpretable  by  this 
hypothesis. 

Parallelism  between  the  courses  of  development  in  species 
allied  by  remote  ancestry,  is  liable  to  be  variously  modi- 
fied in  correspondence  with  the  later  ancestral  forms  passed 
through  after  divergence  of  such  species.  The  substitution 
of  a  direct  for  an  indirect  process  of  formation,  which  we 
have  reason  to  believe  will  show  itself,  must  obscure  the 
embryonic  history.  And  the  principle  of  economy  which 
leads  to  this  substitution  produces  effects  that  are  very  irregu- 
lar and  uncertain  in  consequence  of  the  endlessly  varied  con- 
ditions. Thus  several  causes  conspire  to  produce  deviations 
from  the  general  law. 

Let  it  be  remarked,  finally,  that  the  ability  to  trace  out 
embryologic  kinships  and  the  inability  to  do  this,  occur  just 
where,  according  to  the  hypothesis  of  Evolution,  they  should 
occur.  We  saw  in  §  lOOa  that  zoologists  are  agreed  in  group- 
ing animals  into  some  17  phyla — Mollusca,  Arthropoda, 
Echinodermata,  &c. — each  of  which  includes  a  number  of 
classes  severally  sub-divided  into  orders,  genera,  species.  All 
the  members  of  each  phylum  are  so  related  embryologically, 
that  the  existence  of  a  common  ancestor  of  them  in  the 
remote  past  is  considered  certain.  But  when  it  comes  to  the 
relations  among  the  archaic  ancestors,  opinion  is  unsettled. 
Whether,  for  instance,  the  primitive  Chordata,  out  of  which 
the  Vertebrata  emerged,  have  molluscan  affinities  or  anne- 
lidan  affinities,  is  still  a  matter  in  dispute.  With  regard  to 
the  origins  of  various  other  types  no  settled  conclusions  are 
held.  Now  it  is  clear  that  on  tracing  down  each  branch  of 
the  great  genealogical  tree,  kinships  would  be  much  more 


THE  ARGUMENTS  FROM  EMBRYOLOGY.  467 

manifest  among  the  recently-differentiated  forms  than  aiming 
those  forms  which  diverged  from  one  another  in  the  earl;est 
stages  of  organic  life,  and  had  separated  widely  before  any  of 
the  types  we  now  know  had  come  into  existence. 


T 


CHAPTER  VI. 

THE    ARGUMENTS    FROM    MORPHOLOGY. 


§  133.  LEAVING  out  of  consideration  those  parallelisms 
among  their  modes  of  development  which  characterize 
organisms  belonging  to  each  group,  that  community  of  plan 
which  exists  among  them  when  mature  is  extremely 
remarkable  and  extremely  suggestive.  As  before  shown 
(§  103),  neither  the  supposition  that  these  combinations  of 
attributes  which  unite  classes  are  fortuitous,  nor  the  supposi- 
tion that  no  other  combinations  were  practicable,  nor  the 
supposition  of  adherence  to  pre-determined  typical  plans, 
suffices  to  explain  the  facts.  An  instance  will  best  prepare 
the  reader  for  seeing  the  true  meaning  of  these  fundamental 
likenesses. 

Under  the  immensely-varied  forms  of  insects,  greatly 
elongated  like  the  dragon-fly  or  contracted  in  shape  like  the 
lady-bird,  winged  like  the  butterfly  or  wingless  like  the 
flea,  we  find  this  character  in  common — there  are  primarily 
seventeen  segments.*  These  segments  may  be  distinctly 

*  Early  in  our  friendship  (about  1855)  Prof.  Huxley  expressed  to  me  his 
conviction  that  all  the  higher  articulate  animals  have  twenty  segments  or 
somites.  That  he  adhered  to  this  view  in  1880,  when  his  work  on  The 
Crayfish  was  published,  is  shown  by  his  analysis  there  given  of  the  twenty 
segments  existing  in  this  fluviatile  crustacean ;  and  adhesion  to  it  had  been 
previously  shown  in  1877,  when  his  work  on  The  Anatomy  of  Inveitebrated 
Animals  was  published.  On  p.  398  of  that  work  he  writes : — "  In  the  abdo- 
men there  are,  at  most,  eleven  somites,  none  of  which,  in  the  adult,  bear 
an.bulatory  limbs.  Thus,  assuming  the  existence  of  six  somites  in  the  head, 
4G8 


THE  ARGUMENTS  FROM  MORPHOLOGY.  4G9 

marked  or  they  may  be  so  fused  as  to  make  it  difficult  to  find 
the  divisions  between  them,  but  they  always  exist.  What 
now  can  be  the  meaning  of  this  community  of  structure 
throughout  the  hundred  thousand  kinds  of  insects  filling  the 
air,  burrowing  in  the  earth,  swimming  in  the  water?  Why 
under  the  down-covered  body  of  a  moth  and  under  the  hard 
wing-cases  of  a  beetle,  should  there  be  discovered  the  same 
number  of  divisions?  Why  should  there  be  no  more  somites 
in  the  Stick-insect,  or  other  Phasmid  a  foot  long,  than  there 
are  in  a  small  creature  like  the  louse?  Why  should  the 
inert  Aphis  and  the  swift-flying  Emperor-butterfly  be  con- 
structed on  the  same  fundamental  plan?  It  cannot  be  by 
chance  that  there  exist  equal  numbers  of  segments  in  all 
these  multitudes  of  species.  There  is  no  reason  to  think  it 
was  necessary,  in  the  sense  that  no  other  number  would  have 
made  a  possible  organism.  And  to  say  that  it  is  the  result 
of  design — to  say  that  the  Creator  followed  this  pattern 
throughout,  merely  for  the  purpose  of  maintaining  the  pat- 
tern— is  to  assign  an  absurd  motive.  Xo  rational  interpre- 
tation of  these  and  countless  like  morphological  facts,  can  be 
given  except  by  the  hypothesis  of  evolution;  and  from  the 
hypothesis  of  evolution  they,  are  corollaries.  If  organic  forms 
have  arisen  from  common  stocks  by  perpetual  divergences 
and  re-divergences — if  they  have  continued  to  inherit,  more 
or  less  clearly,  the  characters  of  ancestral  races;  then  there 

the  normal  number  of  somites  in  the  body  of  insects  will  be  twenty,  as  in  the 
higher  Cnmtaiea  and  Arachnida."  To  this  passage,  however,  he  puts  the 
note : — "  It  is  open  to  question  whether  the  podical  plates  represent  a 
somite ;  and  therefore  it  must  be  recollected  that  the  total  number  of 
somites,  the  existence  of  which  can  be  actually  demonstrated  in  insects,  is 
only  seventeen,  viz.,  four  for  the  head,  three  for  the  thorax,  and  ten  for  the 
abdomen."  I  have  changed  the  number  twenty,  which  in  the  original 
edition  occurred  in  the  text,  to  the  number  seventeen  in  deference  to  sug- 
gestions made  to  me;  though  I  find  in  Dr.  Sharp's  careful  and  elaborate 
work  on  the  Insecta,  that  Viallanes  and  Cholodkovsky  agree  with  Huxley  in 
believing  that  there  are  six  somites  in  the  insect-head.  The  existence  of  a 
doubt  on  this  point,  however,  docs  not  essentially  affect  the  argument,  since 
there  is  agreement  among  morphologists  respecting  the  constancy  of  the  total 
number  of  somites  in  insects. 
31 


470  THE  EVOLUTION  OF  LIFE. 

will  naturally  result  these  communities  of  fundamental 
structure  among  creatures  which  have  severally  become 
modified  in  multitudinous  ways  and  degrees,  in  adaptation  to 
their  respective  modes  of  life.  To  this  let  it  be 

added  that  while  the  belief  in  an  intentional  adhesion  to  a 
pre-determined  pattern  throughout  a  whole  group,  is  nega- 
tived by  the  occurrence  of  occasional  deviations  from  the 
pattern;  such  deviations  are  reconcilable  with  the  belief  in 
evolution.  As  pointed  out  in  the  last  chapter,  ancestral 
traits  will  be  obscured  more  or  less  according  as  the  super- 
posed modifications  of  structure,  have  or  have  not  been  fur- 
thered by  the  conditions  of  life  and  development  to  which 
the  type  has  been  subjected. 

§  134.  Besides  these  wide-embracing  and  often  deeply- 
hidden  homologies,  which  hold  together  different  animals, 
there  are  the  scarcely-less  significant  homologies  between  dif- 
ferent organs  of  the  same  animal.  These,  like  the  others, 
are  obstacles  to  the  supernatural  interpretations  and  sup- 
ports of  the  natural  interpretation. 

One  of  the  most  familiar  and  instructive  examples  is 
furnished  by  the  vertebral  column.  Snakes,  which  move 
sinuously  through  and  over  plants  and  stones,  obviously  need 
a  segmentation  of  the  bony  axis  from  end  to  end;  and  inas- 
much as  flexibility  is  required  throughout  the  whole  length 
of  the  body,  there  is  advantage  in  the  comparative  uniformity 
of  this  segmentation.  The  movements  would  be  impeded  if, 
instead  of  a  chain  of  vertebrae  varying  but  little  in  their 
lengths,  there  existed  in  the  middle  of  the  series  some  long 
bony  mass  that  would  not  bend.  But  in  the  higher  Verte- 
brata,  the  mechanical  actions  and  reactions  demand  that 
while  some  parts  of  the  vertebral  column  shall  be  flexible, 
other  parts  shall  be  inflexible.  Inflexibility  is  specially  requi- 
site in  that  part  of  it  called  the  sacrum;  which,  in  mammals 
and  birds,  forms  a  fulcrum  exposed  to  the  greatest  strains 
the  skeleton  has  to  bear.  Now  in  both  mammals  and  birds, 


THE  ARGUMENTS  FROM   MORPHOLOGY.  471 

this  rigid  portion  of  the  vertebral  column  is  not  made  of 
one  long  segment  or  vertebra,  but  of  several  segments  fused 
together.  In  man  there  are  five  of  these  confluent  sacral 
vertebra?;  and  in  the  ostrich  tribe  they  number  from  seven- 
teen to  twenty.  Why  is  this?  Why,  if  the  skeleton  of  each 
species  was  separately  contrived,  was  this  bony  mass  made 
by  soldering  together  a  number  of  vertebra  like  those  forming 
the  rest  of  the  column,  instead  of  being  made  out  of  one 
single  piece?  And  why,  if  typical  uniformity  was  to  be 
maintained,  does  the  number  of  sacral  vertebrae  vary  within 
the  same  order  of  birds?  Why,  too,  should  the  development 
of  the  sacrum  be  by  the  round-about  process  of  first  forming 
its  separate  constituent  vertebra,  and  then  destroying  their 
separateness  ?  In  the  embryo  of  a  mammal  or  bird,  the 
central  element  of  the  vertebral  column  is,  at  the  outset, 
continuous.  The  segments  that  are  to  become  vertebrae, 
arise  gradually  in  the  adjacent  mesoderm,  and  enwrap  this 
originally-homogeneous  axis  or  notochord.  Equally  in  those 
parts  of  the  spine  which  are  to  remain  flexible,  and  in  those 
parts  which  are  to  grow  rigid,  these  segments  are  formed; 
and  that  part  of  the  spine  which  is  to  compose  the  sacrum, 
having  acquired  this  segmental  structure,  loses  it  again  by 
coalescence  of  the  segments.  To  what  end  is  this  construc- 
tion and  re-construction?  If,  originally,  the  spine  in  verte- 
brate animals  consisted  from  head  to  tail  of  separate  move- 
able  segments,  as  it  does  still  in  fishes  and  some  reptiles — if, 
in  the  evolution  of  the  higher  Vertebrata,  certain  of  these 
moveable  segments  were  rendered  less  moveable  with  respect 
to  one  another,  by  the  mechanical  conditions  they  were 
exposed  to,  and  at  length  became  relatively  immovable;  it 
is  comprehensible  why  the  sacrum  formed  out  of  them, 
should  continue  ever  after  to  show  its  originally-segmented 
structure.  But  on  any  other  hypothesis  this  segmented 
structure  is  inexplicable.  "  We  see  the  same  law 

in  comparing  the  wonderfully  complex  jaws  and  legs  in  crus- 
taceans," says  Mr.  Darwin:  referring  to  the  fact  that  those 


472  THE  EVOLUTION  OF  LIFE. 

numerous  lateral  appendages  which,  in  the  lower  crustaceans, 
most  of  them  serve  as  legs,  and  have  like  shapes,  are,  in  the 
higher  crustaceans,  some  of  them  represented  by  enormously- 
developed  claws,  and  others  by  variously-modified  foot-jaws. 
"  It  is  familiar  to  almost  every  one,"  he  continues,  "  that  in 
a  flower  the  relative  position  of  the  sepals,  petals,  stamens, 
and  pistils,  as  well  as  their  intimate  structure,  are  intelli- 
gible on  the  view  that  they  consist  of  metamorphosed 
leaves  arranged  in  a  spire.  In  monstrous  plants  we  often 
get  direct  evidence  of  the  possibility  of  one  organ  being 
transformed  into  another;  and  we  can  actually  see  in 
embryonic  crustaceans  and  in  many  other  animals,  and  in 
flowers,  that  organs,  which  when  mature  become  extremely 
different,  are  at  an  early  stage  of  growth  exactly  alike." 
.  .  .  "  Why  should  one  crustacean,  which  has  an  ex- 
tremely complex  mouth  formed  of  many  parts  consequently 
always  have  fewer  legs;  or  conversely,  those  with  many  legs 
have  simpler  mouths?  Why  should  the  sepals,  petals, 
stamens,  and  pistils  in  any  individual  flower,  though  fitted 
for  such  widely-different  purposes,  be  all  constructed  on  the 
same  pattern  ?  " 

To  these  and  countless  similar  questions,  the  theory  of 
evolution  furnishes  the  only  rational  answer.  In  the  course 
of  that  change  from  homogeneity  to  heterogeneity  of  struc- 
ture displayed  in  evolution  under  every  form,  it  will  neces- 
sarily happen  that  from  organisms  made  up  of  numerous  like 
parts,  there  will  arise  organisms  made  lip  of  parts  more  and 
more  unlike:  which  unlike  parts  will  nevertheless  continue 
to  bear  traces  of  their  primitive  likeness. 

§  135.  One  more  striking  morphological  fact,  near  akin 
to  some  of  the  facts  dwelt  on  in  the  last  chapter,  must  be 
here  set  down — the  frequent  occurrence,  in  adult  animals 
and  plants,  of  rudimentary  and  useless  organs,  which  are 
homologous  with  organs  that  are  developed  and  useful  in 
allied  animals  and  plants.  In  the  last  chapter  we  saw  that 


THE  ARGUMENTS  FROM  MORPHOLOGY.  473 

during  the  development  of  embryos,  there  often  arise  organs 
which  disappear  on  being  replaced  by  other  organs  dis- 
charging the  same  functions  .  in  better  ways ;  and  that  in 
some  cases,  organs  develop  to  certain  points  and  are  then 
re-absorbed  without  performing  any  functions.  Very  gene- 
rally, however,  the  partially-developed  organs  are  retained 
throughout  life. 

The  osteology  of  the  higher  Vertebrata  supplies  abundant 
examples.  Vertebral  processes  which,  in  one  tribe,  are  fully 
formed  and  ossified  from  independent  centres,  are,  in  other 
tribes,  mere  tubercles  not  having  independent  centres  of 
ossification.  While  in  the  tail  of  this  animal  the  vertebras 
are  severally  composed  of  centrum  and  appendages,  in  the 
tail  of  that  animal  they  are  simple  osseous  masses  without 
any  appendages;  and  in  another  animal  they  have  lost  their 
individualities  by  coalescence  with  neighbouring  vertebra? 
into  a  rudimentary  tail.  From  the  structures  of  the  limbs 
analogous  facts  are  cited  by  comparative  anatomists.  The 
undeveloped  state  of  certain  metacarpal  bones,  characterizes 
whole  groups  of  mammals.  In  one  case  we  find  the  normal 
number  of  digits;  and,  in  another  case,  a  smaller  number 
with  an  atrophied  digit  to  make  out  the  complement.  Here  is 
a  digit  with  its  full  number  of  phalanges ;  and  there  a  digit  of 
which  one  phalange  has  been  arrested  in  its  growth.  Still 
more  remarkable  are  the  instances  of  entire  limbs  being  rudi- 
mentary; as  in  certain  snakes,  which  have  hind  legs  hidden 
beneath  the  integument.  So,  too,  is  it  with  dermal 

appendages.  Some  of  the  smooth-skinned  amphibia  have 
scales  buried  in  the  skin.  The  seal,  which  is  a  mammal  con- 
siderably modified  in  adaptation  to  an  aquatic  life,  and  which 
uses  its  feet  mainly  as  paddles,  has  toes  that  still  bear  ex- 
ternal nails;  but  the  manatee,  which  is  a  much  more  trans- 
formed mammal,  has  nailless  paddles  which,  when  the  skin  is 
removed,  are  said,  by  Humboldt,  to  display  rudimentary  nails 
at  the  ends  of  the  imbedded  digits.  Nearly  all  birds  are 
covered  with  developed  feathers,  severally  composed  of  a  shaft 


474  THE  EVOLUTION  OP  LIFE. 

bearing  fibres,  each  of  which,  again,  bears  a  fringe  of  down. 
But  in  some  birds,  as  in  the  ostrich,  various  stages  of 
arrested  development  of  the  feathers  may  be  traced :  between 
the  unusually-elaborated  feathers  of  the  tail,  and  those  about 
the  beak  which  are  reduced  to  simple  hairs,  there  are  transi- 
tions. Nor  is  this  the  extreme  case.  In  the  Apteryx  we  see 
the  whole  of  the  feathers  reduced  to  a  hair-like  form.  Again, 
the  hair  which  commonly  covers  the  body  in  mammals  is, 
over  the  greater  part  of  the  human  body  almost  rudimentary, 
and  is  in  some  parts  reduced  to  mere  down — down  which 
nevertheless  proves  itself  to  be  homologous-  with  the  hair  of 
mammals  in  general,  by  occasionally  developing  into  the 
original  form.  Numerous  cases  of  aborted  organs  are  given 
by  Mr.  Darwin,  of  which  a  few  may  be  here  added.  "  No- 
thing can  be  plainer,"  he  remarks,  "than  that  wings  are 
formed  for  flight,  yet  in  how  many  insects  do  we  see  wings  so 
reduced  in  size  as  to  be  utterly  incapable  of  flight,  and  not 
rarely  lying  under  wing-cases,  firmly  soldered  together  ?**... 
"  In  plants  with  separated  sexes,  the  male  flowers  often  have 
a  rudiment  of  a  pistil ;  and  Kolreuter  found  that  by  crossing 
such  male  plants  with  an  hermaphrodite  species,  the  rudi- 
ment of  the  pistil  in  the  hybrid  offspring  was  much  increased 
in  size ;  and  this  shows  that  the  rudiment  and  the  perfect  pistil 
are  essentially  alike  in  nature."  And  then,  to  complete  the 
proof  that  these  undeveloped  parts  are  marks  of  descent  from 
races  in  which  they  were  developed,  there  are  not  a  few  direct 
experiences  of  this  relation.  "  We  have  plenty  of  cases  of 
rudimentary  organs  in  our  domestic  productions — as  the 
stump  of  a  tail  in  tailless  breeds — the  vestige  of  an  ear  in 
earless  breeds — the  re-appearance'  of  minute  dangling  horns 
in  hornless  breeds  of  cattle."  (Origin  of  Species,  1859,  pp. 
451,454.) 

Here,  as  before,  the  teleological  doctrine  fails  utterly;  for 
these  rudimentary  organs  are  useless,  and  occasionally  even 
detrimental;  as  is  the  appendix  vermiformis,  in  Man — a  part 
of  the  caecum  which  is  of  no  value  for  the  purpose  of  absorp- 


THE  ARGUMENTS  FROM   MORPHOLOGY.  475 

tion  but  which,  by  detaining  small  foreign  bodies,  often  causes 
severe  inflammation  and  death.  The  doctrine  of  typical  plans 
is  equally  out  of  court;  for  while,  in  some  members  of  a 
group,  rudimentary  organs  completing  the  general  type  are 
traceable,  in  other  members  of  the  same  group  such  organs 
are  unrepresented.  There  remains  only  the  doctrine  of  evolu- 
tion; and  to  this,  these  rudimentary  organs  offer  no  diffi- 
culties. On  the  contrary,  they  are  among  its  most  striking 
evidences. 

§  136.  The  general  truths  of  morphology  thus  coincide  in 
their  implications.  Unity  of  type,  maintained  under  extreme 
dissimilarities  of  form  and  mode  of  life,  is  explicable  as  re- 
sulting from  descent  with  modification;  but  is  otherwise  in- 
explicable. The  likenesses  disguised  by  unlikenesses,  which 
the  comparative  anatomist  discovers  between  various  organs 
in  the  same  organism,  are  worse  than  meaningless  if  it  be 
supposed  that  organisms  were  severally  framed  as  we  now 
see  them;  but  they  fit  in  quite  harmoniously  with  the  belief 
that  each  kind  of  organism  is  a  product  of  accumulated  modi- 
fications upon  modifications.  And  the  presence,  in  all  kinds 
of  animals  and  plants,  of  functionally-useless  parts  corre- 
sponding to  parts  that  are  functionally-useful  in  allied  ani- 
mals and  plants,  while  it  is  totally  incongruous  with  the  belief 
in  a  construction  of  each  organism  by  miraculous  interposi- 
tion, is  just  what  we  are  led  to  expect  by  the  belief  that  organ- 
isms have  arisen  by  progression. 


CHAPTER  VII. 

THE    ARGUMENTS    FROM    DISTRIBUTION. 

§137.  IN  §§105  and  106,  we  contemplated  the  phenomena 
of  distribution  in  Space.  The  general  conclusions  reached, 
in  great  part  based  on  the  evidence  brought  together  by  Mr. 
Darwin,  were  that,  "  on  the  one  hand,  we  have  similarly-con- 
ditioned, and  sometimes  nearly-adjacent,  areas,  occupied  by 
quite  different  Faunas.  On  the  other  hand,  we  have  areas 
remote  from  each  other  in  latitude,  and  contrasted  in  soil  as 
well  as  climate,  which  are  occupied  by  closely-allied  Faunas." 
Whence  it  was  inferred  that  "  as  like  organisms  are  not  uni- 
versally, or  even  generally,  found  in  like  habitats;  nor  very 
unlike  organisms,  in  very  unlike  habitats ;  there  is  no  manifest 
pre-determined  adaptation  of  the  organisms  to  the  habitats." 
In  other  words,  the  facts  of  distribution  in  Space  do  not 
conform  to  the  hypothesis  of  design.  At  the  same 

time  we  saw  that  "  the  similar  areas  peopled  by  dissimilar 
forms,  are  those  between  which  there  are  impassable  barriers ; 
while  the  dissimilar  areas  peopled  by  similar  forms,  are  those 
between  which  there  are  no  such  barriers ; "  and  these 
generalizations  appeared  to  harmonize  with  the  abundantly- 
illustrated  truth,  "  that  each  species  of  organism  tends  ever 
to  expand  its  sphere  of  existence — to  intrude  on  other  areas, 
other  modes  of  life,  other  media." 

By  way  of  showing  still  more  clearly  the  effects  of  com- 
petition among  races  of  organisms,  let  me  here  add  some 
476 


THE  ARGUMENTS  FROM   DISTRIBUTION.  477 

recently-published  instances  of  the  usurpations  of  areas,  and 
changes  of  distribution  hence  resulting.  In  the  Natural  His- 
tory Review  for  January,  1864,  Dr.  Hooker  quotes  as  follows 
from  some  New  Zealand  naturalists : — "  You  would  be  sur- 
prised at  the  rapid  spread  of  European  and  other  foreign 
plants  in  this  country.  All  along  the  sides  of  the  main  lines  of 
road  through  the  plains,  a  Polygonum  (aviculare),  called 
'  Cow  Grass,'  grows  most  luxuriantly,  the  roots  sometimes  two 
feet  in  depth,  and  the  plants  spreading  over  an  area  from  four 
to  five  feet  in  diameter.  The  dock  (Rumex  obtusifolius  or  R. 
crispus)  is  to  be  found  in  every  river  bed,  extending  into  the 
valleys  of  the  mountain  rivers,  until  these  become  mere  tor- 
rents. The  sow-thistle  is  spread  all  over  the  country,  growing 
luxuriantly  nearly  up  to  6000  feet.  The  water-cress  increases 
in  our  still  rivers  to  such  an  extent,  as  to  threaten  to  choke 
them  altogether  ...  I  have  measured  stems  twelve  feet 
long  and  three-quarters  of  an  inch  in  diameter.  In  some  of 
the  mountain  districts,  where  the  soil  is  loose,  the  white  clover 
is  completely  displacing  the  native  grasses,  forming  a  close 

sward In  fact,  the  young  native  vegetation  appears 

to  shrink  from  competition  with  these  more  vigorous  in- 
truders." "The  native  (Maori)  saying  is  'as  the  white 
man's  rat  has  driven  away  the  native  rat,  so  the  European 
fly  drives  away  our  own,  and  the  clover  kills  our  fern,  so 
will  the  Maoris  disappear  before  the  white  man  himself.' " 

Given  this  universal  tendency  of  the  superior  to  over- 
run the  habitats  of  the  inferior,*  let  us  consider  what,  on 
the  hypothesis  of  evolution,  will  be  the  effects  on  the  geo- 
graphical relationships  of  species. 

§  138.  A  race  of  organisms  cannot  expand  its  sphere  of 
existence  without  subjecting  itself  to  new  external  conditions. 
Those  of  its  members  which  spread  over  adjacent  areas, 
*  To  avoid  circumlocution  I  let  these  words  stand,  though  they  are  not 
truly  descriptive;  for  the  prosperity  of  imported  species  is  largely,  if  not 
mainly,  caused  by  the  absence  of  those  natural  enemies  which  kept  them  down 
at  home. 


478  THE  EVOLUTION  OF  LIFE. 

inevitably  come  in  contact  with  circumstances  partially 
different  from  their  previous  circumstances;  and  such  of 
them  as  adopt  the  habits  of  other  organisms,  necessarily 
experience  re-actions  more  or  less  contrasted  with  the  re- 
actions before  experienced.  Now  if  changes  of  organic 
structure  are  caused,  directly  or  indirectly,  by  changes  in 
the  incidence  of  forces;  there  must  result  unlikenesses  of 
structure  between  the  divisions  of  a  race  which  colonizes 
new  habitats.  Hence,  in  the  absence  of  obstacles  to  migra- 
tion, we  may  anticipate  manifest  kinships  between  the  ani- 
mals and  plants  of  one  area,  and  those  of  areas  adjoining 
it.  This  inference  corresponds  with  an  induction  before 
set  down  (§  106).  In  addition  to  illustrations  of  it  already 
quoted  from  Mr.  Darwin,  his  pages  furnish  others.  One 
is  that  species  which  inhabit  islands  are  allied  to  species 
which  inhabit  neighbouring  main  lands;  and  another  is 
that  the  faunas  of  clustered  islands  show  marked  similari- 
ties. "  Thus  the  several  islands  of  the  Galapagos  Archi- 
pelago are  tenanted,"  says  Mr.  Darwin,  "  in  a  quite 
marvellous  manner,  by  very  closely  related  species;  so  that 
the  inhabitants  of  each  separate  island,  though  mostly  dis- 
tinct, are  related  in  an  incomparably  closer  degree  to  each 
other  than  to  the  inhabitants  of  any  other  part  of  the  world." 
Mr.  Wallace  has  traced  "  variation  as  specially  influenced  by 
locality  "  among  the  Papilionidce  inhabiting  the  East  Indian 
Archipelago :  showing  how  "  the  species  and  varieties  of 
Celebes  possess  a  striking  character  in  the  form  of  the  an- 
terior wings,  different  from  that  of  the  allied  species  and 
varieties  of  all  the  surrounding  islands ; "  and  how  "  tailed 
species  in  India  and  the  western  islands  lose  their  tails  as 
they  spread  eastward  through  the  archipelago."  During 
his  travels  on  the  Upper  Amazons,  Mr.  Bates  found  that 
u  the  greater  part  of  the  species  of  Ithomice  changed  from 
one  locality  to  another,  not  further  removed  than  100  to  200 
miles ; "  that  "  many  of  these  local  species  have  the  appear- 
ance of  being  geographical  varieties ;  "  and  that  in  some 


THE  ARGUMENTS  FROM   DISTRIBUTION.  479 

species  "  most  of  the  local  varieties  are  connected  with  their 
parent  form  by  individuals  exhibiting  all  the  shades  of 
variation." 

Further  general  relationships  are  to  be  inferred.  If 
races  of  organisms,  ever  being  thrust  by  pressure  of  popula- 
tion into  new  habitats,  undergo  modifications  of  structure  as 
they  diverge  more  and  more  widely  in  Space,  it  follows  that, 
speaking  generally,  the  widest  divergences  in  Space  will 
indicate  the  longest  periods  during  which  the  descendants 
from  a  common  stock  have  been  subject  to  modifying  con- 
ditions; and  hence  that,  among  organisms  of  the  same 
group,  the  smaller  contrasts  of  structure  will  be  limited 
to  the  smaller  areas.  This  we  find:  "varieties  being," 
as  Dr.  Hooker  says  in  his  Flora  of  Tasmania,  "  more  re- 
stricted in  locality  than  species,  and  these  again  than 
genera."  Again,  if  races  of  organisms  spread,  and 

as  they  spread  are  altered  by  changing  incident  forces;  it 
follows  that  where  the  incident  forces  vary  greatly  within 
given  areas,  the  alterations  will  be  more  numerous  than  in 
equal  areas  which  are  less-variously  conditioned.  This,  too, 
proves  to  be  the  fact.  Dr.  Hooker  points  out  that  the  rela- 
tively uniform  regions  have  the  fewest  species;  while  in  the 
most  multiform  regions  the  species  are  the  most  numerous. 

§  139.  Let  us  consider  next,  how  the  hypothesis  of  evo- 
lution corresponds  with  the  facts  of  distribution,  not  over 
different  areas  but  through  different  media.  If  all  forms  of 
organisms  have  descended  from  some  primordial  form,  it 
follows  that  since  this  primordial  form  must  have  inhabited 
some  one  medium  out  of  the  several  media  now  inhabited, 
the  peopling  of  other  media  by  its  descendants  implies 
migration  from  one  medium  to  others — implies  adaptations 
to  media  quite  unlike  the  original  medium.  To  speak  speci- 
fically— water  being  the  medium  in  which  the  lowest  living 
forms  exist,  the  implication  is  that  the  earth  and  the  air 
have  been  colonized  from  the  water.  Great  difficulties 


4SO  THE  EVOLUTION  OF  LIFE. 

appear  to  stand  in  the  way  of  this  assumption.  Ridiculing 
those  who  alleged  the  uniscrial  development  of  organic  forms, 
who,  indeed,  laid  themselves  open  to  ridicule  by  their  many 
untenable  propositions,  Von  Baer  writes — "  A  fish,  swimming 
towards  the  shore  desires  to  take  a  walk,  but  finds  his  fins 
useless.  They  diminish  in  breadth  for  want  of  use,  and  at 
the  same  time  elongate.  This  goes  on  with  children  and 
grandchildren  for  a  few  millions  of  years,  and  at  last  who 
can  be  astonished  that  the  fins  become  feet?  It  is  still 
more  natural  that  the  fish  in  the  meadow,  finding  no  water, 
should  gape  after  air,  thereby,  in  a  like  period  of  time 
developing  lungs;  the  only  difficulty  being  that  in  the 
meanwhile,  a  few  generations  must  manage  without  breath- 
ing at  all."  Though,  as  thus  presented,  the  belief 
in  a  transition  looks  laughable;  and  though  such  deriva- 
tion of  terrestrial  vertebrates  by  direct  modification  of 
piscine  vertebrates,  is  untenable;  yet  we  must  not  conclude 
that  no  migrations  of  the  kind  alleged  can  have  taken  place. 
The  adage  that  "  truth  is  stranger  than  fiction,"  applies  quite 
as  much  to  Nature  in  general  as  to  human  life.  Besides  the 
fact  that  certain  fish  actually  do  "  take  a  walk  "  without  any 
obvious  reason;  and  besides  the  fact  that  sundry  kinds  of 
fish  ramble  about  on  land  when  prompted  by  the  drying-up  of 
the  waters  they  inhabit ;  there  is  the  still  more  astounding  fact 
that  one  kind  of  fish  climbs  trees.  Few  things  seem  more 
manifestly  impossible,  than  that  a  water-breathing  creature 
without  efficient  limbs,  should  ascend  eight  or  ten  feet  up  the 
trunk  of  a  palm;  and  yet  the  Anabas  scandens  does  as  much. 
To  previous  testimonies  on  this  point  Capt.  Mitchell  has 
recently  added  others.  Such  remarkable  cases  of  temporary 
changes  of  media,  will  prepare  us  for  conceiving  how,  under 
special  conditions,  permanent  changes  of  media  may  have 
taken  place;  and  for  considering  how  the  doctrine  of  evolu- 
tion is  elucidated  by  them. 

Inhabitants  of  the  sea,  of  rivers,  and  of  lakes,  are  many 
of  them  left  from  time  to  time  partially  or  completely  with- 


THE  ARGUMENTS  FROM   DISTRIBUTION.  481 

out  water;  and  those  which  show  the  power  to  change 
their  media  temporarily  or  permanently,  are  in  very 
many  cases  of  the  kinds  most  liable  to  be  thus  deserted  by 
their  medium.  Let  us  consider  what  the  sea-shore  shows 
us.  Twice  a  day  the  rise  and  the  fall  of  the  tide  covers 

and  uncovers  plants  and  animals,  fixed  and  moving;  and 
through  the  alternation  of  spring  and  neap  tides,  it  results 
that  the  exposure  of  the  organisms  living  low  down  on  the 
beach,  varies  both  in  frequency  and  duration:  while  some  of 
them  are  left  dry  only  once  a  fortnight  for  a  very  short  time, 
others,  a  little  higher  up,  are  left  dry  during  two  or  three 
hours  at  several  ebb  tides  every  fortnight.  Then  by  small 
gradations  we  come  to  such  as,  living  at  the  top  of  the  beach, 
are  bathed  by  salt-water  only  at  long  intervals;  and  still 
higher  to  some  which  are  but  occasionally  splashed  in  stormy 
weather.  What,  now,  do  we  find  among  the  organisms  thus 
subject  to  various  regular  and  irregular  alterations  of 
media?  Besides  many  plants  and  many  fixed  animals,  we 
find  moving  animals  of  numerous  kinds;  some  of  which  are 
confined  to  the  lower  zones  of  this  littoral  region,  but  others 
of  which  wander  over  the  whole  of  it.  Omitting  the  humbler 
types,  it  will  suffice  to  observe  that  each  of  the  two  great 
sub-kingdoms,  Mollusca  and  Arthropoda,  supplies  examples  of 
creatures  having  a  wide  excursiveness  within  this  region. 
We  have  gasteropods  which,  when  the  tide  is  down,  habitu- 
ally creep  snail-like  over  sand  and  sea-weed,  even  up  as  far 
as  high-water  mark.  We  have  several  kinds  of  crustaceans, 
of  which  the  crab  is  the  most  conspicuous,  running  about  on 
the  wet  beach,  and  sometimes  rambling  beyond  the  reach  of 
the  water.  And  then  note  the  striking  fact  that  each  of  the 
forms  thus  habituated  to  changes  of  media,  is  allied  to  forms 
which  are  mainly  or  wholly  terrestrial.  On  the  West  Coast 
of  Ireland  marine  gasteropods  are  found  on  the  rocks  thre? 
hundred  feet  above  the  sea,  where  they  are  only  at  long  in- 
tervals wetted  by  the  spray;  and  though  between  gasteropod- 
of  this  class  and  land-gasteropods  the  differences  are  con- 


482  THE  EVOLUTION  OF  LIFE. 

siderablc,  yet  the  land-gasteropods  arc  more  closely  allied  to 
them  than  to  any  other  Mollusca.  Similarly,  the  two  highest 
orders  of  crustaceans  have  their  species  which  live  occasion- 
ally, or  almost  entirely,  out  of  the  water:  there  is  a  kind  of 
lobster  in  the  Mauritius  which  climbs  trees ;  and  there  is  the 
land-crab  of  the  West  Indies,  which  deserts  the  sea  when  it 
reaches  maturity  and  re-visits  it  only  to  spawn.  Seeing, 
thus,  how  there  are  many  kinds  of  marine  creatures  whose 
habitats  expose  them  to  frequent  changes  of  media;  how 
some  of  the  higher  kinds  so  circumstanced,  show  a  consider- 
able adaptation  to  both  media;  and  how  these  amphibious 
kinds  are  allied  to  kinds  that  are  mainly  or  wholly  terres- 
trial; we  shall  see  that  the  migrations  from  one  medium  to 
another,  which  evolution  pre-supposes,  are  by  no  means  im- 
practicable. With  such  evidence  before  us,  the  assumption 
that  the  distribution  of  the  Vertebrata  through  media  so  dif- 
ferent as  air  and  water,  may  have  been  gradually  effected  in 
some  analogous  manner,  would  not  be  altogether  unwarranted 
even  had  we  no  clue  to  the  process.  We  shall  find,  however, 
a  tolerably  distinct  clue.  Though  rivers,  and  lakes, 

and  pools,  have  no  sensible  tidal  variations,  they  have  their 
rises  and  falls,  regular  and  irregular,  moderate  and  extreme. 
Especially  in  tropical  climates,  we  see  them  annually  full 
for  a  certain  number  of  months,  and  then  dwindling  away 
and  drying  up.  The  drying  up  may  reach  various  degrees 
and  last  for  various  periods.  It  may  go  to  the  extent  only 
of  producing  a  liquid  mud,  or  it  may  reduce  the  mud  to  a 
hardened,  fissured  solid.  It  may  last  for  a  few  days  or  for 
months.  That  is  to  say,  aquatic  forms  which  are  in  one 
place  annually  subject  to  a  slight  want  of  water  for  a  short 
time,  are  elsewhere  subject  to  greater  wants  for  longer  times : 
we  have  gradations  of  transition,  analogous  to  those  which 
the  tides  furnish.  Now  it  is  well  known  that  creatures  in- 
habiting such  waters  -have,  in  various  degrees,  powers  of 
meeting  these  contingencies.  The  contained  fish  either  bury 
themselves  in  the  mud  when  the  dry  season  comes,  or  ramble 


THE  ARGUMENTS  FROM  DISTRIBUTION.  483 

in  search  of  other  waters.  This  is  proved  by  evidence  from 
India,  Guiana,  Siam,  Ceylon ;  and  some  of  these  fish,  as  the 
Anabas  scandens,  are  known  to  survive  for  days  out  of  the 
water.  But  the  facts  of  greatest  significance  are  furnished 
by  an  allied  class  of  Vertebrata,  almost  peculiar  to  habitats  of 
this  kind.  The  Amphibia  are  not,  like  fish,  usually  found  in 
waters  that  are  never  partially  or  wholly  dried  up;  but  they 
nearly  all  inhabit  waters  which,  at  certain  seasons,  evaporate, 
in  great  measure  or  completely — waters  in  which  most  kinds 
of  fish  cannot  exist.  And  what  are  the  leading  structural 
traits  of  these  Amphibia?  They  have  two  respiratory 
systems — pulmonic  and  branchial — variously  developed  in 
different  orders;  and  they  have  two  or  four  limbs,  also 
variously  developed.  Further,  the  class  Amphibia  consists  of 
two  groups,  in  one  of  which  this  duality  of  the  respiratory 
system  is  permanent,  and  the  development  of  the  limbs 
always  incomplete;  and  in  the  other  of  which  the  branchiae 
disappear  as  the  lungs  and  limbs  become  fully  developed. 
The  lowest  group,  the  Perennibranchiata,  have  internal 
organs  for  aerating  the  blood  which  approach  in  various 
degrees  to  lungs,  until  "  in  the  Siren,  the  pulmonic  respira- 
tion is  more  extensive  and  important  than  the  branchial ; " 
and  to  these  creatures,  having  a  habitat  partially  aerial  and 
partially  aquatic,  there  are  at  the  same  time  supplied,  in  the 
shallow  water  covering  soft  mud,  the  mechanical  conditions 
which  render  swimming  difficult  and  rudimentary  limbs  use- 
ful. In  the  higher  group,  the  Caducibranchiata,  we  find  still 
more  suggestive  transformations.  Having  at  first  a  structure 
resembling  that  which  is  permanent  in  the  perennibranchiate 
amphibian,  the  larva  of  the  caducibranchiate  amphibian 
pursues  for  a  time  a  similar  life;  but,  eventually,  while  the 
branchial  appendages  dwindle  the  lungs  grow :  the  respiration 
of  air,  originally  supplementary  to  the  respiration  of  water, 
predominates  over  it  more  and  more,  till  it  replaces  it  entirely ; 
and  an  additional  pair  of  legs  is  produced.  This  having  been 
done,  the  creature  either  becomes,  like  the  Triton,  one  which 


484  THE  EVOLUTION  OP  LIFE. 

quits  the  water  only  occasionally;  or,  like  the  Frog,  one 
which  pursues  a  life  mainly  terrestrial,  and  returns  to  the 
water  now  and  then.  Finally,  if  we  ask  under  what  condi- 
tions this  metamorphosis  of  a  water-breather  into  an  air- 
breather  completes  itself,  the  answer  is — it  completes  itself 
at  the  time  when  the  shallow  pools  inhabited  by  the  larvae 
are  being  dried  up,  or  in  danger  of  being  dried  up,  by  the 
summer's  sun.* 

See,  then,  how  significant  are  the  facts  when  thus  brought 
together.  There  are  particular  habitats  in  which  animals  are 
subject  to  changes  of  media.  In  such  habitats  exist  animals 
having,  in  various  degrees,  the  power  to  live  in  both  media, 
consequent  on  various  phases  of  transitional  organization. 
Near  akin  to  these  animals  there  are  some  that,  after  passing 
their  early  lives  in  the  water,  acquire  more  completely  the 
structures  fitting  them  to  live  on  land,  to  which  they  then 
migrate.  Lastly,  we  have  closely-allied  creatures,  like  the 
Surinam  toad  and  the  terrestrial  salamander,  which,  though 
they  belong  by  their  structures  to  the  class  Amphibia,  are 
not  amphibious  in  their  habits — creatures  the  larvae  of  which 
do  not  pass  their  early  lives  in  the  water,  and  yet  go  through 
these  same  metamorphoses!  Must  we  then  think,  like 
Von  Baer,  that  the  distribution  of  kindred  organisms  through 
different  media  presents  an  insurmountable  difficulty?  On 
the  contrary,  with  facts  like  these  before  us,  the  evolution- 
hypothesis  supplies  possible  interpretations  of  many  phe- 
nomena that  are  else  unaccountable.  After  seeing  the  ways 
in  which  such  changes  of  media  are  in  some  cases  gradually 

*  While  these  pages  are  passing  through  the  press  (in  1864),  Dr.  Hooker 
has  obliged  me  by  pointing  out  that  "plants  afford  many  excellent  examples" 
of  analogous  transitions.  He  says  that  among  true  "water  plants,"  there 
are  found,  in  the  same  species,  varieties  which  have  some  leaves  submerged 
and  some  floating ;  other  varieties  in  which  they  are  all  floating ;  and  other 
varieties  in  which  they  are  all  submerged.  Further,  that  many  plants 
characterized  by  floating  leaves,  and  which  have  all  their  leaves  floating  when 
they  grow  in  deeper  water,  are  found  with  partly  aerial  leaves  when  they  grow 
in  shallower  water ;  and  that  elsewhere  they  occur  in  almost  dry  soil  with  all 
their  leaves  aerial. 


THE  ARGUMENTS  FROM  DISTRIBUTION.  485 

imposed  by  physical  conditions,  and  in  other  cases  voluntarily 
commenced  and  slowly  increased  in  the  search  after  food; 
we  shall  begin  to  understand  how,  in  the  course  of  evolution, 
there  have  arisen  strange  obscurations  of  one  type  by  the 
externals  of  another  type.  When  we  see  land-birds  occa- 
sionally feeding  by  the  water-side,  and  then  learn  that  one  of 
them,  the  water-ouzel,  an  "  anomalous  member  of  the  strictly 
terrestrial  thrush  family,  wholly  subsists  by  diving — grasp- 
ing the  stones  with  its  feet  and  using  its  wings  under  water  " 
— we  are  enabled  to  comprehend  how,  under  pressure  of 
population,  aquatic  habits  may  be  acquired  by  creatures 
organized  for  aerial  life ;  and  how  there  may  eventually  arise 
an  ornithic  type  in  which  the  traits  of  the  bird  are  very 
much  disguised.  On.  finding  among  mammals  some  that,  in 
search  of  prey  or  shelter,  have  taken  to  the  water  in  various 
degrees,  we  shall  cease  to  be  perplexed  on  discovering  the 
mammalian  structure  hidden  under  a  fish-like  form,  as  it  is 
in  the  Cetacea  and  the  Sirema:  especially  on  finding  that  in 
the  sea-lion  and  the  seals  there  are  transitional  forms.  Grant 
that  there  has  ever  been  going  on  that  re-distribution  of 
organisms  which  we  see  still  resulting  from  their  intrusions 
on  one  another's  areas,  media,  and  modes  of  life;  and  we 
have  an  explanation  of  those  multitudinous  cases  in  which 
homologies  of  structure  are  complicated  with  analogies.  And 
while  it  accounts  for  the  occurrence  in  one  medium  of  organic 
types  fundamentally  organized  for  another  medium,  the  doc- 
trine of  evolution  accounts  also  for  the  accompanying  unfit- 
nesses.  Either  the  seal  has  descended  from  some  mammal 
which  little  by  little  became  aquatic  in  its  habits,  in  which 
case  the  structure  of  its  hind  limbs  has  a  meaning;  or  else  it 
was  specially  framed  for  its  present  habitat,  in  which  case 
the  structure  of  its  hind  limbs  is  incomprehensible. 

§  140.  The  facts  respecting  distribution  in  Time,  which 
have  more  than  any  others  been  cited  both  in  proof  and  in 
disproof  of  evolution,  are  too  fragmentary  to  be  conclusive 


486  THE  EVOLUTION  OF  LIFE. 

either  way.  Were  the  geological  record  complete,  or  did  it, 
as  both  Uniformitarians  and  Progressionists  have  commonly 
assumed,  give  us  traces  of  the  earliest  organic  forms;  the 
evidence  hence  derived,  for  or  against,  would  have  had  more 
weight  than  any  other  evidence.  As  it  is,  all  we  can  do  is  to 
see  whether  such  fragmentary  evidence  as  remains,  is  con- 
gruous with  the  hypothesis. 

Palaeontology  has  shown  that  there  is  a  "  general  relation 
between  lapse  of  time  and  divergence  of  organic  forms " 
(§  107) ;  and  that  "  this  divergence  is  comparatively  slow  and 
continuous  where  there  is  continuity  in  the  geological  forma- 
tions, but  is  sudden  and  comparatively  wide  wherever  there 
occurs  a  great  break  in  the  succession  of  strata."  Now  this 
is  obviously  what  we  should  expect.  The  hypothesis  implies 
structural  changes  that  are  not  sudden  but  gradual.  Hence, 
where  conformable  strata  indicate  a  continuous  record,  we 
may  anticipate  successions  of  forms  only  slightly  different 
from  one  another;  while  we  may  rationally  look  for  marked 
contrasts  between  the  groups  of  forms  fossilized  in  adjacent 
strata,  where  there  is  evidence  of  a  great  blank  in  the  record. 

The  permanent  disappearances  of  species,  of  genera,  and 
of  orders,  which  we  saw  to  be  a  fact  tolerably-well  established, 
is  also  a  fact  for  which  the  belief  in  evolution  prepares  us. 
If  later  organic  forms  have  in  all  cases  descended  from 
earlier  organic  forms,  and  have  diverged  during  their  descent, 
both  from  their  prototypes  and  from  one  another;  then  it 
follows  that  such  of  them  as  become  extinct  at  any  epoch, 
will  never  re-appear  at  a  subsequent  epoch;  since  there  can 
never  again  arise  a  concurrence  and  succession  of  conditions 
such  as  those  under  which  each  type  was  evolved. 

Though  comparisons  of  ancient  and  modern  organic  forms, 
prove  that  many  types  have  persisted  through  enormous 
periods  of  time,  without  undergoing  great  changes;  it  was 
shown  that  such  comparisons  do  not  disprove  the  occurrence 
in  other  organic  forms,  of  changes  great  enough  to  produce 
what  are  called  different? ty.pes.v.- The -result  of  inductive  in- 


THE  ARGUMENTS  FROM   DISTRIBUTION.  457 

quiry  we  saw  to  be,  that  while  a  few  modern  higher  types  yield 
signs  of  having  been  developed  from  ancient  lower  types; 
and  that  while  there  are  many  modern  types  which  may  have 
been  thus  developed,  though  we  are  without  evidence  that 
they  have  been  so ;  yet  that  "  any  admissible  hypothesis  of 
progressive  modification  must  be  compatible  with  persistence 
without  progression  through  indefinite  periods."  Now  these 
results  are  quite  congruous  with  the  hypothesis  of  evolution. 
As  rationally  interpreted,  evolution  must  in  all  cases  be  under- 
stood to  result,  directly  or  indirectly,  from  the  incidence  of 
forces.  If  there  are  no  changes  of  conditions  entailing  organic 
changes,  organic  changes  are  not  to  be  expected.  Only  in 
organisms  which  fall  under  conditions  leading  to  additional 
modifications  answering  to  additional  needs,  will  there  be 
that  increased  heterogeneity  which  characterizes  higher  forms. 
Hence,  though  the  facts  of  paleontology  cannot  be  held  con- 
clusive proof  of  evolution,  yet  they  are  congruous  with  it; 
and  some  of  them  yield  it  strong  support. 

§  141.  One  general  truth  respecting  distribution  in  Time, 
is  profoundly  significant.  If,  instead  of  contemplating  the 
relations  among  past  forms  of  life  taken  by  themselves,  we 
contemplate  the  relations  between  them  and  the  forms  now 
existing,  we  find  a  connexion  which  is  in  harmony  with  the 
belief  in  evolution  but  irreconcilable  with  any  other  belief. 

Note,  first,  how  full  of  meaning  is  the  close  kinship 
existing  between  the  aggregate  of  organisms  now  living,  and 
the  aggregate  of  organisms  which  lived  in  the  most  recent 
geologic  times.  In  the  last-formed  strata,  nearly  all  the 
imbedded  remains  are  those  of  species  which  still  flourish. 
Strata  a  little  older  contain  a  few  fossils  of  species  now  ex- 
tinct, though,  usually,  species  greatly  resembling  extant  ones. 
Of  the  remains  found  in  strata  of  still  earlier  date,  the  ex- 
tinct species  form  a  larger  percentage ;  and  the  differences  be- 
tween them  and  the  allied  species  now  living  are  more  marked. 
That  is  to  say,  the  gradual  change  of  organic  types  in  Time, 


488  THE  EVOLUTION  CF  LIFE. 

which  we  hefore  saw  is  indicated  by  the  geological  record,  ia 
equally  indicated  hy  the  relation  between  existing  organic 
types  and  organic  types  of  the  epochs  preceding  our  own. 
The  evidence  completely  accords  with  the  belief  in  a  descent 
of  present  life  from  past  life.  Doubtless  such  a 

kinship  is  not  incongruous  with  the  doctrine  of  special  crea- 
tions. It  may  be  argued  that  the  introduction,  from  time  to 
time,  of  new  species  better  fitted  to  the  somewhat  changed 
conditions  of  the  Earth's  surface,  would  result  in  an  apparent 
alliance  between  our  living  Flora  and  Fauna,  and  the  Floras 
and  Faunas  that  lately  lived.  No  one  can  deny  it.  But  on 
passing  from  the  most  general  aspect  of  the  alliance  to  its 
more  special  aspects,  we  shall  find  this  interpretation  com- 
pletely negatived. 

For  besides  a  close  kinship  between  the  aggregate  of  sur- 
viving forms  and  the  aggregate  of  forms  which  have  died  out 
in  recent  geologic  times;  there  is  a  peculiar  connexion  of 
like  nature  between  present  and  past  forms  in  each  great 
geographical  region.  The  instructive  fact,  before  cited  from 
Mr.  Darwin,  is  the  "  wonderful  relationship  in  the  same  con- 
tinent between  the  dead  and  the  living."  This  relationship 
is  not  explained  by  the  supposition  that  new  species  have 
been  at  intervals  supernaturally  placed  in  each  habitat,  as  the 
habitat  became  modified;  since,  as  we  saw,  species  are  by  no 
means  uniformly  found  in  the  habitats  to  which  they  are  best 
adapted.  It  cannot  be  said  that  the  marsupials  imbedded  in 
recent  Australian  strata,  having  become  extinct  because  of 
unfitness  to  some  new  external  condition,  the  existing  mar- 
supials were  then  specially  created  to  fit  the  modified  en- 
vironment; since  sundry  animals  found  elsewhere  are  so 
much  more  in  harmony  with  these  new  Australian  condi- 
tions that,  when  taken  to  Australia,  they  rapidly  extrude  the 
marsupials.  While,  therefore,  the  similarity  between  the 
existing  Australian  Fauna  and  the  Fauna  which  immediately 
preceded  it  over  the  same  area,  is  just  that  which  the  belief 
in  evolution  leads  us  to  expect;  it  is  a  similarity  which 


THE  ARGUMENTS  FROM   DISTRIBUTION.  489 

cannot  be  otherwise  accounted  for.    And  so  is  it  with  parallel 
relations  in  New  England,  in  South  America,  and  in  Europe. 

§  142.  Given,  then,  that  pressure  which  species  exercise 
on  one  another,  in  consequence  of  the  universal  overfilling 
of  their  respective  habitats — given  the  resulting  tendency  to 
thrust  themselves  into  one  another's  areas,  and  media,  and 
modes  of  life,  along  such  lines  of  least  resistance  as  from 
time  to  time  are  found — given  besides  the  changes  in  modes 
of  life,  hence  arising,  those  other  changes  which  physical 
alterations  of  habitats  necessitate — given  the  structural  modi- 
fications directly  or  indirectly  produced  in  organisms  by  modi- 
fied conditions;  and  the  facts  of  distribution  in  Space  and 
Time  are  accounted  for.  That  divergence  and  re-divergence 
of  organic  forms,  which  we  saw  to  be  shadowed  forth  by  the 
truths  of  classification  and  the  truths  of  embryology,  we  see 
to  be  also  shadowed  forth  by  the  truths  of  distribution.  If 
that  aptitude  to  multiply,  to  spread,  to  separate,  and  to  dif- 
ferentiate, which  the  human  races  have  in  all  times  shown, 
be  a  tendency  common  to  races  in  general,  as  we  have  ample 
reason  to  assume;  then  there  will  result  those  kinds  of  spacial 
relations  and  chronological  relations  among  the  species,  and 
genera,  and  orders,  peopling  the  Earth's  surface,  which  we 
find  exist.  The  remarkable  identities  of  type  discovered 
between  organisms  inhabiting  one  medium,  and  strangely 
modified  organisms  inhabiting  another  medium,  are  at  the 
same  time  rendered  comprehensible.  And  the  appear- 
ances and  disappearances  of  species  which  the  geological 
record  shows  us,  as  well  as  the  connexions  between  succes- 
sive groups  of  species  from  early  eras  down  to  our  own,  cease 
to  be  inexplicable. 


CHAPTER  VIII. 

HOW    IS    ORGANIC    EVOLUTION    CAUSED? 

§  143.  ALREADY  it  has  been  necessary  to  speak  of  the 
causes  of  organic  evolution  in  general  terms;  and  now  we 
are  prepared  for  considering  them  specifically.  The  task 
before  us  is  to  affiliate  the  leading  facts  of  organic  evolu- 
tion, on  those  same  first  principles  conformed  to  by  evolution 
at  large. 

Before  attempting  this,  however,  it  will  be  instructive  to 
glance  at  the  causes  of  organic  evolution  which  have  been 
from  time  to  time  alleged. 

§  144.  The  theory  that  plants  and  animals  of  all  kinds 
were  gradually  evolved,  seems  to  have  been  at  first  accom- 
panied only  by  the  vaguest  conception  of  cause — or  rather, 
by  no  conception  of  cause  properly  so  called,  but  only  by  the 
blank  form  of  a  conception.  One  of  the  earliest  who  in 
modern  times  (1735)  contended  that  organisms  are  indefi- 
nitely modifiable,  and  that  through  their  modifications  they 
have  become  adapted  to  various  modes  of  existence,  was 
De  Maillet.  But  though  De  Maillet  supposed  all  living 
beings  to  have  arisen  by  a  natural,  continuous  process,  ho 
does  not  appear  to  have  had  any  definite  idea  of  that  which 
determines  this  process.  In  1794,  in  his  Zoonomia, 

Dr.  Erasmus  Darwin  gave  reasons    (sundry  of  them  valid 
ones)  for  believing  that  organized  beings  of  every  kind,  have 
490 


HOWVIS  ORGANIC  EVOLUTION  CAUSED!  491 

descended  from  one,  or  a  few,  primordial  germs;  and  along 
with  some  observable  causes  of  modification,  which  he  points 
out  as  aiding  the  developmental  process,  he  apparently 
ascribes  it,  in  part,  to  a  tendency  given  to  such  germ  or 
germs  when  created.  He  suggests  the  possibility  "that  all 
warm-blooded  animals  have  arisen  from  one  living  filament, 
which  THE  GREAT  FIRST  CAUSE  endued  with  animality,  with 
the  power  of  acquiring  new  parts,  attended  with  new  pro- 
pensities, directed  by  irritations,  sensations,  volitions,  and 
associations;  and  thus  possessing  the  faculty  of  continuing 
to  improve  by  its  own  inherent  activity."  In  this  passage 
we  see  the  idea  to  be,  that  evolution  is  pre-determined 
by  some  intrinsic  proclivity.  "  It  is  curious,"  says 

Mr.  Charles  Darwin,  "how  largely  my  grandfather,  Dr. 
Erasmus  Darwin,  anticipated  the  erroneous  grounds  of 
opinion,  and  the  views  of  Lamarck."  One  of  the  anticipa- 
tions was  this  ascription  of  development  to  some  inherent 
tendency.  To  the  "  plan  general  de  la  nature,  et  sa  marche 
uniforme  dans  ses  operations,"  Lamarck  attributes  "  la 
progression  evidente  qui  existe  dans  la  composition  de 
1'organisation  des  animaux ;  "  and  "  la  gradation  reguliere 
qu'ils  devroient  offrir  dans  la  composition  de  leur  organ- 
isation," he  thinks  is  rendered  irregular  by  secondary 
causes.  Essentially  the  same  in  kind,  though  some- 

what different  in  form,  is  the  conception  put  forth  in  the 
Vestiges  of  Creation;  the  author  of  which  contends  "  that 
the  several  series  of  animated  beings,  from  the  simplest  and 
oldest  up  to  the  highest  and  most  recent,  are,  under  the  pro- 
vidence of  God,  the  results,  first,  of  an  impulse  which  has 
been  imparted  to  the  forms  of  life,  advancing  them,  in  defi- 
nite times,  by  generation,  through  grades  of  organization 
terminating  in  the  highest  dicotyledons  and  vertebrata ; " 
and  that  the  progression  resulting  from  these  impulses,  is 
modified  by  certain  other  causes.  The  broad  contrasts  be- 
tween lower  and  higher  forms  of  life,  are  regarded  by  him 
as  implying  an  innate  aptitude  to  give  birth  to  forms  of 


492  THE  EVOLUTION  OF  LIFE. 

more   perfect   structures.  The   last   to    re-enunciate 

this  doctrine  has  been  Prof.  Owen ;  who  asserts  "  the  axiom 
of  the  continuous  operation  of  creative  power,  or  of  the 
ordained  becoming  of  living  things."  Though  these  words 
do  not  suggest  a  very  definite  idea,  yet  they  indicate  the 
belief  that  organic  progress  is  a  result  of  some  in-dwelling 
tendency  to  develop,  supernaturally  impressed  on  living 
matter  at  the  outset — some  ever-acting  constructive  force 
which,  independently  of  other  forces,  moulds  organisms  into 
higher  and  higher  forms. 

In  whatever  way  it  is  formulated,  or  by  whatever  language 
it  is  obscured,  this  ascription  of  organic  evolution  to  some 
aptitude  naturally  possessed  by  organisms,  or  miraculously 
imposed  on  them,  is  unphilosophical.  It  is  one  of  those  ex- 
planations which  explain  nothing — a  shaping  of  ignorance 
into  the  semblance  of  knowledge.  The  cause  assigned  is  not 
a  true  cause — not  a  cause  assimilable  to  known  causes — not 
a  cause  that  can  be  anywhere  shown  to  produce  analogous 
effects.  It  is  a  cause  unrepresentable  in  thought:  one  of 
those  illegitimate  symbolic  conceptions  \diich  cannot  by  any 
mental  process  be  elaborated  into  a  real  conception.  In 
brief,  this  assumption  of  a  persistent  formative  power  in- 
herent in  organisms,  and  making  them  unfold  into  higher 
types,  is  an  assumption  no  more  tenable  than  the  assump- 
tion of  special  creations:  of  which,  indeed,  it  is  but  a  modi- 
fication; differing  only  by  the  fusion  of  separate  unknown 
processes  into  a  continuous  unknown  process. 

§  145.  Besides  this  intrinsic  tendency  to  progress  which 
Dr.  Darwin  ascribes  to  animals,  he  says  they  have  a  capacity 
for  being  modified  by  processes  which  their  own  desires 
initiate.  He  speaks  of  powers  as  "  excited  into  action  by 
the  necessities  of  the  creatures  which  possess  them,  and  on 
which  their  existence  depends ; "  and  more  specifically  he 
says  that  "from  their  first  rudiment  or  primordium,  to  the 
termination  of  their  lives,  all  animals  undergo  perpetual 


HOW  IS  ORGANIC  EVOLUTION  CAUSED!  493 

transformations;  which  are  in  part  produced  by  their  own 
exertions,  in  consequence  of  their  desires  and  aversions,  of 
their  pleasures  and  their  pains,  or  of  irritations,  or  of  associa- 
tions; and  many  of  these  acquired  forms  or  properties  are 
transmitted  to  their  posterity."  While  it  embodies  a  belief 
for  which  much  may  be  said,  this  passage  involves  the 
assumption  that  desires  and  aversions,  existing  before  ex- 
periences of  the  actions  to  which  they  are  related,  were  the 
originators  of  the  actions,  and  therefore  of  the  structural 
modifications  caused  by  them.  In  his  Philosophic 

Zoologique,  Lamarck  much  more  specifically  asserts  "  le 
sentiment  interieur"  to  be  in  all  creatures  that  have  developed 
nervous  systems,  an  independent  cause  of  those  changes  of 
form  which  are  due  to  the  exercise  of  organs :  distinguishing 
it  from  that  simple  irritability  possessed  by  inferior  animals, 
which  cannot  produce  what  we  call  a  desire  or  emotion;  and 
holding  that  these  last,  along  with  all  "qui  manquent  de 
systeme  nerveux,  ne  vivent  qu'a  1'aide  des  excitations  qu'ils 
regoivent  de  Fexterieur."  Afterwards  he  says — "  je  reconnus 
que  la  nature,  obligee  d'abord  d'emprunter  des  milieux  en- 
vironnans  la  puissance  excitatrice  des  mouvemens  vitaux  et 
des  actions  des  animaux  imparfaits,  sut,  en  composant  de 
plus  en  plus  1'organisation  animale,  transporter  cette  puis- 
sance dans  Finterieur  meme  de  ces  etres,  et  qu'a  la  fin,  elle 
parvint  a  mettre  cette  meme  puissance  a  la  disposition  de 
Findividu."  And  still  more  definitely  he  contends  that  if 
one  considers  "  la  progression  qui  se  montre  dans  la  com- 
position de  Forganisation,"  .  .  .  "  alors  on  eut  pu  aperce- 
voir  comment  les  besoins.,  d'abord  reduits  a  nullite,  et  dont 
le  nombre  ensuite  s'est  accru  graduellement,  ont  amene  le 
penchant  aux  actions  propres  a  y  satisfaire:  comment  les 
actions  devenues  habituelles  et  energiques,  ont  occasionne  le 
developpement  des  organes  qui  les  executent." 

Now  though  this  conception  of  Lamarck  is  more  precisely 
stated,  and  worked  out  with  much  greater  elaboration  and 
wider  knowledge  of  the  facts,  it  is  essentially  the  same  as 


494  THE  EVOLUTION  OP  LIFE. 

that  of  Dr.  Darwin;  and  along  with  the  troth  it  contain*, 
contains  also  the  same  error  more  distinctly  pronounced. 
Merely  noting  that  desires  or  wants,  acting  directly  only 
on  the  nervo-muscular  system,  can  have  no  immediate  in- 
fluence on  very  many  organs,  as  the  viscera,  or  inch  external 
appendages  as  hair  and  feathers;  and  observing,  further, 
that  even  some  parts  which  belong  to  the  apparatus  of  ex- 
ternal action,  such  as  the  bones  of  the  skull,  cannot  be  made 
to  grow  by  increase  of  function  called  forth  by  desire;  it 
will  suffice  to  point  out  that  the  difficulty  is  not  solved,  but 
simply  slurred  over,  when  needs  or  wants  are  introduced  as 
independent  causes  of  evolution.  True  though  it  is,  as  Dr. 
Darwin  and  Lamarck  contend,  that  desires,  by  leading  to 
increased  actions  of  motor  organs,  may  induce  further  de- 
velopments of  such  organs;  and  true,  as  it  probably  is,  that 
the  modifications  hence  arising  are  transmissible  to  offspring; 
yet  there  remains  the  unanswered  question — Whence  do  these 
desires  originate?  The  transference  of  the  exciting  power 
from  the  exterior  to  the  interior,  as  described  by  Lamarck, 
begs  the  question.  How  comes  there  a  wish  to  perform  an 
action  not  before  performed?  Until  some  beneficial  result 
has  been  felt  from  going  through  certain  movements,  what 
can  suggest  the  execution  of  such  movements?  Every  desire 
consists  primarily  of  a  mental  representation  of  that  which 
is  desired,  and  secondarily  excites  a  mental  representation  of 
the  actions  by  which  it  is  attained;  and  any  such  mental 
representations  of  the  end  and  the  means,  imply  antecedent 
experience  of  the  end  and  antecedent  use  of  the  means.  To 
assume  that  in  the  course  of  evolution  there  from  time  to 
time  arise  new  kinds  of  actions  dictated  by  new  desires,  is 
simply  to  remove  the  difficulty  a  step  back. 

§  146.  Changes  of  external  conditions  are  named,  by  Dr. 
Darwin,  as  causes  of  modifications  in  organisms.  Assigning 
as  evidence  of  original  kinship,  that  marked  similarity  of 
type  which  exists  among  animals,  he  regards  their  devia* 


HOW  IS  ORGANIC  EVOLUTION  CAUSED!  495 

tions  from  one  another,  as  caused  by  differences  in  their 
modes  of  life:  such  deviations  being  directly  adaptive. 
After  enumerating  various  appliances  for  procuring  food,  he 
says  they  all  "  seem  to  have  been  gradually  produced  during 
many  generations  by  the  perpetual  endeavour  of  the  creatures 
to  supply  the  want  of  food,  and  to  have  been  delivered  to 
their  posterity  with  constant  improvement  of  them  for  the 
purposes  required."  And  the  creatures  possessing  these 
various  appliances  are  considered  as  having  been  rendered 
unlike  by  seeking  for  food  in  unlike  ways.  As  illustrating 
the  alterations  wrought  by  changed  circumstances,  he  names 
the  acquired  characters  of  domestic  animals.  La- 

marck has  elaborated  the  same  view  in  detail:  using  for  the 
purpose,  with  great  ingenuity,  his  extensive  knowledge  of 
the  animal  kingdom.  From  a  passage  in  the  Avertiissement 
it  would  at  first  sight  seem  that  he  looks  upon  direct  adapt- 
ation to  new  conditions  as  the  chief  cause  of  evolution.  He 
says — "Je  regardai  comme  certain  que  le  mouvement  des 
fluides  dans  Finterieur  des  animaux,  mouvement  qui  c'est 
progressivement  accelere  avec  la  composition  plus  grande  de 
1'organisation ;  et  que  I'influence  des  circonstances  nouvelles, 
a  mesure  que  les  animaux  s'y  exposerent  en  se  repandant 
dans  tous  les  lieux  habitables,  furent  les  deux  causes  gene- 
rales  qui  ont  amene  les  differens  animaux  a  1'etat  ou  nous  les 
voyons  actuellement."  But  elsewhere  the  view  he  expresses 
appears  decidedly  different  from  this.  He  asserts  that  "  dans 
sa  marche,  la  nature  a  commence,  et  recommence  encore  tous 
les  jours,  par  former  les  corps  organises  les  plus  simples ; " 
and  that  "  les  premieres  ebauches  de  1'animal  et  du  vegetal 
etant  formees  dans  les  lieux  et  les  circonstances  convenables, 
les  facultes  d'une  vie  commengante  et  d'un  mouvement  or- 
ganique  etabli,  ont  necessairement  developpe  peu  a  peu  les 
organes,  et  qu'avec  le  temps  elles  les  ont  diversifies  ainsi  que 
les  parties."  And  then,  further  on,  he  puts  in  italics  this 
proposition : — "  La  progression  dans  la  composition  de  I 'or- 
ganisation subit,  Qa  et  la,  dans  la  serie  generale  des  animaux, 


496  THE  EVOLUTION  OF  LIFE. 

des  anomalies  operees  par  I' influence  des  circonstances  d' habi- 
tation, et  par  celle  des  habitudes  contractees."  These,  and 
sundry  other  passages,  joined  with  his  general  scheme  of 
classification,  make  it  clear  that  Lamarck  conceived  adaptive 
modification  to  be,  not  the  cause  of  progression,  but  the  cause 
of  irregularities  in  progression.  The  inherent  tendency 
which  organisms  have  to  develop  into  more  perfect  forms, 
would,  according  to  him,  result  in  a  uniform  series  of  forms ; 
but  varieties  in  their  conditions  work  divergences  of  struc- 
ture, which  break  up  the  series  into  groups :  groups  which 
he  nevertheless  places  in  uni-serial  order,  and  regards  as  still 
substantially  composing  an  ascending  succession. 

§  147.  These  speculations,  crude  as  they  may  be  con- 
sidered, show  much  sagacity  in  their  respective  authors,  and 
have  done  good  service.  Without  embodying  the  truth  in 
definite  shapes,  they  contain  adumbrations  of  it.  Not 
directly,  but  by  successive  approximations,  do*  mankind 
reach  correct  conclusions;  and  those  who  first  think  in  the 
right  direction,  loose  as  may  be  their  reasonings,  and  wide  of 
the  mark  as  their  inferences  may  be,  yield  indispensable 
aid  by  framing  provisional  conceptions  and  giving  a  bent  to 
inquiry. 

Contrasted  with  the  dogmas  of  his  age,  the  idea  of  De 
Maillet  was  a  great  advance.  Before  it  can  be  ascertained 
how  organized  beings  have  been  gradually  evolved,  there 
must  be  reached  the  conviction  that  they  have  been  gradu- 
ally evolved;  and  this  conviction  he  reached.  His  wild 
notions  about  the  way  in  which  natural  causes  acted  in  the 
production  of  plants  and  animals,  must  not  make  us  forget 
the  merit  of  his  intuition  that  animals  and  plants  were  pro- 
duced by  natural  causes.  In  Dr.  Darwin's  brief  expo- 
sition, the  belief  in  a  progressive  genesis  of  organisms  is 
joined  with  an  interpretation  having  considerable  definite- 
ness  and  coherence.  In  the  space  of  ten  pages  he  not  only 
indicates  several  of  the  leading  classes  of  facts  which  support 


HOW  IS  ORGANIC  EVOLUTION  CAUSED!  497 

the  hypothesis  of  development,  but  he  does  something  towards 
suggesting  the  process  of  development.  His  reasonings  show 
an  unconscious  mingling  of  the  belief  in  a  supernaturally- 
impressed  tendency  to  develop,  with  the  belief  in  a  develop- 
ment arising  from  the  changing  incidence  of  conditions. 
Probably  had  he  pursued  the  inquiry  further,  this  last  belief 
would  have  grown  at  the  expense  of  the  first.  La- 

marck, in  elaborating  this  general  conception,  has  given 
greater  precision  both  to  its  truth  and  to  its  error.  Assert- 
ing the  same  imaginary  factors  and  the  same  real  factors,  he 
has  traced  out  their  supposed  actions  in  detail;  and  has,  in 
consequence,  committed  himself  to  a  greater  number  of 
untenable  positions.  But  while,  in  trying  to  reconcile  the 
facts  with  a  theory  which  is  only  an  adumbration  of  the 
truth,  he  laid  himself  open  to  the  criticisms  of  his  con- 
temporaries; he  proved  himself  profounder  than  his  con- 
temporaries by  seeing  that  natural  genesis,  however  caused, 
has  been  going  on.  If  they  were  wise  in  not  indorsing  a 
theory  which  fails  to  account  for  a  great  part  of  the  facts; 
they  were  unwise  in  ignoring  that  degree  of  congruity  with 
the  facts,  which  shows  the  theory  to  contain  some  funda- 
mental verity. 

Leaving  out,  however,  the  imaginary  factors  of  evolution 
which  these  speculations  allege,  and  looking  only  at  the  one 
actual  factor  which  Dr.  Darwin  and  Lamarck  assign  as  ac- 
counting for  some  of  the  phenomena;  it  is  manifest,  from 
our  present  stand-point,  that  this,  so  far  as  it  is  a  cause  of 
evolution,  is  a  proximate  cause  and  not  an  ultimate  cause. 
To  say  that  functionally-produced  adaptation  to  conditions 
originates  either  evolution  in  general,  or  the  irregularities  of 
evolution,  is  to  raise  the  further  question — why  is  there  a 
functionally-produced  adaptation  to  conditions? — why  do 
use  and  disuse  generate  appropriate  changes  of  structure? 
Neither  this  nor  any  other  interpretation  of  biologic  evolu- 
tion which  rests  simply  on  the  basis  of  biologic  induction,  is 
an  ultimate  interpretation.  The  biologic  induction  must 


498  THE  EVOLUTION  OP  LIFE. 

itself  be  interpreted.  Only  when  the  process  of  evolution  of 
organisms  is  affiliated  on  the  process  of  evolution  in  general, 
can  it  be  truly  said  to  be  explained.  The  thing  required  is 
to  show  that  its  various  results  are  corollaries  from  first 
principles.  We  have  to  reconcile  the  facts  with  the  universal 
laws  of  the  re-distribution  of  matter  and  motion. 


CHAPTER   IX. 

EXTERNAL    FACTORS. 

§  148.  WHEN  illustrating  the  rhythm  of  motion  (First 
Principles,  §  83)  it  was  pointed  out  that  besides  the  daily 
and  annual  alternations  in  the  quantities  of  light  and  heat 
which  any  portion  of  the  Earth's  surface  receives  from  the 
Sun,  there  are  alternations  which  require  immensely-greater 
periods  to  complete.  Eeference  was  made  to  the  fact  that 
"  every  planet,  during  a  certain  long  period,  presents  more  of 
its  northern  than  of  its  southern  hemisphere  to  the  Sun  at  the 
time  of  its  nearest  approach  to  him;  and  then  again,  during 
a  like  period,  presents  more  of  its  southern  hemisphere  than 
of  its  northern — a  recurring  coincidence  which,  though  it 
causes  in  some  planets  no  sensible  alterations  of  climate,  in- 
volves, in  the  case  of  the  Earth,  an  epoch  of  21,000  years 
during  which  each  hemisphere  goes  through  a  cycle  of  tem- 
perate seasons,  and  seasons  that  are  extreme  in  their  heat 
and  cold."  Further,  we  saw  that  there  is  a  variation  of  this 
variation.  The  slow  rhythm  of  temperate  and  intemperate 
climates,  which  takes  21,000  years  to  complete  itself,  under- 
goes exaggeration  and  mitigation  during  epochs  that  are  far 
longer.  The  Earth's  orbit  slowly  alters  in  form :  now  ap- 
proximating to  a  circle,  and  now  becoming  more  eccentric. 
During  the  period  in  which  the  Earth's  orbit  has  least 
eccentricity,  the  temperate  and  intemperate  climates  which 
repeat  their  cycle  in  21,000  years,  are  severally  less  tern- 


500  THE  EVOLUTION  OP  LIFE. 

perate  and  less  intemperate,  than  when,  some  one  or  two 
millions  of  years  later,  the  Earth's  orbit  has  reached  its  ex- 
treme of  eccentricity. 

Thus,  besides  those  daily  variations  in  the  quantities  of 
light  and  heat  received  by  organisms,  and  responded  to  by 
variations  in  their  functions;  and  besides  the  annual  variations 
in  the  quantities  of  light  and  heat  which  organisms  receive, 
and  similarly  respond  to  by  variations  in  their  functions; 
there  are  variations  that  severally  complete  themselves  in 
21,000  years  and  in  some  millions  of  years — variations  to 
which  there  must  also  be  responses  in  the  changed  functions 
of  organisms.  The  whole  vegetal  and  animal  kingdoms, 
are  subject  to  quadruply-compounded  rhythms  in  the  inci- 
dence of  the  forces  on  which  life  primarily  depends — 
rhythms  so  involved  in  their  slow  working  round  that  at  no 
time  during  one  of  these  vast  epochs,  can  the  incidence 
of  these  various  forces  be  exactly  the  same  as  at  any  other 
time.  To  the  direct  effects  so  produced  on  organ- 

isms, have  to  be  added  much  more  important  indirect  effects. 
Changes  of  distribution  must  result.  Certain  redistributions 
are  occasioned  even  by  the  annual  variations  in  the  quantities 
of  the  solar  rays  received  by  each  part  of  the  Earth's  surface. 
The  migrations  of  birds  thus  caused  are  familiar.  So,  too, 
are  the  migrations  of  certain  fishes:  in  some  cases  from  one 
part  of  the  sea  to  another;  in  some  cases  from  salt  water 
to  fresh  water;  and  in  some  cases  from  fresh  water  to  salt 
water.  Now  just  as  the  yearly  changes  in  the  amounts  of 
light  and  heat  falling  on  each  locality,  yearly  extend  and 
restrict  the  habitats  of  many  organisms  which  are  able  to 
move  about  with  some  rapidity;  so  must  the  alterations  of 
temperate  and  intemperate  climates  produce  extensions  and 
restrictions  of  habitats.  These,  though  slow,  must  be  uni- 
versal— must  affect  the  habitats  of  stationary  organisms  as 
well  as  those  of  locomotive  ones.  For  if,  during  an  astro- 
nomic era,  there  is  going  on  at  any  limit  to  a  plant's  habitat, 
a  diminution  of  the  winter's  cold  or  summer's  heat,  which 


EXTERNAL  FACTORS.  501 

had  before  stopped  its  spread  at  that  limit ;  then,  though  the 
individual  plants  are  fixed,  yet  the  species  will  move:  the 
seeds  of  plants  living  at  the  limit,  will  produce  individuals 
which  survive  beyond  the  limit.  The  gradual  spread  so 
effected,  having  gone  on  for  some  ten  thousand  years,  the 
opposite  change  of  climate  will  begin  to  cause  retreat.  The 
tide  of  each  species  will,  during  one  half  of  a  long  epoch, 
slowly  flow  into  new  regions,  and  then  will  slowly  ebb  away 
from  them.  Further,  this  rise  and  fall  in  the  tide  of  each 
species  will,  during  far  longer  intervals,  undergo  increasing 
rises  and  falls  and  then  decreasing  rises  and  falls.  There 
will  be  an  alteration  of  spring  tides  and  neap  tides,  answer- 
ing to  the  changing  eccentricity  of  the  Earth's  orbit. 

These  astronomical  rhythms,  therefore,  entail  on  organisms 
unceasing  changes  in  the  incidence  of  forces  in  two  ways. 
They  directly  subject  them  to  variations  of  solar  influences, 
in  such  a  manner  that  each  generation  is  somewhat  differently 
affected  in  its  functions;  and  they  indirectly  bring  about 
complicated  alterations  in  the  environing  agencies,  by  carry- 
ing each  species  into  the  presence  of  new  physical  conditions, 
new  soil  and  surface. 

§  149.  The  power  of  geological  actions  to  modify  every- 
where the  circumstances  in  which  plants  and  animals  are 
placed,  is  conspicuous.  In  each  locality  denudation  slowly 
uncovers  different  deposits,  and  slowly  changes  the  exposed 
areas  of  deposits  already  uncovered.  Simultaneously,  the 
alluvial  beds  in  course  of  formation,  are  qualitatively  affected 
by  these  progressive  changes  in  the  natures  and  proportions  of 
the  strata  denuded.  The  inclinations  of  surfaces  and  their 
directions  with  respect  to  the  Sun,  are  at  the  same  time  modi- 
fied; and  the  organisms  existing  on  them  are  thus  having 
their  thermal  conditions  continually  altered,  as  well  as  their 
drainage.  Igneous  action,  too,  complicates  these  gradual 
modifications.  A  flat  region  cannot  be  step  by  step  thrust 
up  into  a  protuberance  without  unlike  climatic  changes 


502  THE  EVOLUTION  OP  LIFE. 

being  produced  in  its  several  parts,  by  their  exposures  to 
different  aspects.  Extrusions  of  trap,  wherever  they  take 
place,  revolutionize  the  localities ;  both  over  the  areas  covered 
and  over  the  areas  on  to  which  their  detritus  is  carried.  And 
where  volcanoes  are  formed,  the  ashes  they  occasionally  send 
out  modify  the  character  of  the  soil  throughout  large  sur- 
rounding tracts. 

In  like  manner  alterations  in  the  Earth's  crust  cause  the 
ocean  to  be  ever  subjecting  the  organisms  it  contains  to  new 
combinations  of  conditions.  Here  the  water  is  being  deep- 
ened by  subsidence,  and  there  shallowed  by  upheaval.  While 
the  falling  upon  it  of  sediment  brought  down  by  neighbour- 
ing large  rivers,  is  raising  the  sea-bottom  in  one  place,  in 
another  the  habitual  rush  of  the  tide  is  carrying  away  the 
sediment  deposited  in  past  times.  The  mineral  character  of 
the  submerged  surface  on  which  sea-weeds  grow  and  molluscs 
crawl,  is  everywhere  occasionally  changed;  now  by  the 
bringing  away  from  an  adjacent  shore  some  previously  un- 
touched strata;  and  now  by  the  accumulation  of  organic 
remains,  such  as  the  shells  of  pteropods  or  of  foraminifera. 
A  further  series  of  alterations  in  the  circumstances  of  marine 
organisms,  is  entailed  by  changes  in  the  movements  of  the 
water.  Each  modification  in  the  outlines  of  neighbouring 
shores  makes  the  tidal  streams  vary  their  directions  or 
velocities  or  both.  And  the  local  temperature  is  from  time 
to  time  raised  or  lowered,  because  some  far-distant  change 
of  form  in  the  Earth's  crust  has  wrought  a  divergence  in  those 
circulating  currents  of  warm  and  cold  water  which  pervade 
the  ocean. 

These  geologically-caused  changes  in  the  physical  charac- 
ters of  each  environment,  occur  in  ever-new  combinations, 
and  with  ever-increasing  complexity.  As  already  shown 
(First  Principles,  §  158),  it  follows  from  the  law  of  the  mul- 
tiplication of  effects,  that  during  long  periods  each  tract  of 
the  Earth's  surface  increases  in  heterogeneity  of  both  form 
and  substance.  So  that  plants  and  animals  of  all  kinds  are, 


EXTERNAL  FACTORS.  503 

in  the  course  of  generations,  subjected  by  alterations  in  the 
crust  of  the  Earth,  to  sets  of  incident  forces  differing  from 
previous  sets,  both  by  changes  in  the  proportions  of  the 
factors  and,  occasionally,  by  the  addition  of  new  factors. 

§150.  Variations  in  the  astronomical  conditions  joined 
with  variations  in  the  geological  conditions,  bring  about 
variations  in  the  meteorological  conditions.  Those  slow 
alternations  of  elevation  and  subsidence  which  take  place 
over  immense  areas,  here  producing  a  continent  where  once 
there  was  a  fathomless  ocean,  and  there  causing  wide  seas 
to  spread  where  in  a  long  past  epoch  there  stood  snow- 
capped mountains,  gradually  work  great  atmospheric  changes. 
While  the  highest  parts  of  an  emerging  surface  of  the 
Earth's  crust  exist  as  a  cluster  of  islands,  the  plants  and 
animals  which  in  course  of  time  migrate  to  them  have 
climates  that  are  peculiar  to  small  tracts  of  land  surrounded 
by  large  tracts  of  water.  As,  by  successive  upheavals, 
greater  areas  are  exposed,  there  begin  to  arise  sensible  con- 
trasts between  the  states  of  their  peripheral  parts  and  their 
central  parts.  The  breezes  which  daily  moderate  the 
extremes  of  temperature  near  the  shores,  cease  to  affect 
the  interiors;  and  the  interiors,  less  qualified  too  in  their 
heat  and  cold  by  such  ocean-currents  as  approach  the  coast, 
acquire  more  decidedly  the  characters  due  to  their  latitudes. 
Along  with  the  further  elevations  which  unite  the  members 
of  the  archipelago  into  a  continent,  there  come  new  meteoro- 
logic  changes,  as  well  as  exacerbations  of  the  old.  The 
winds,  which  were  comparatively  uniform  in  their  directions 
and  periods  when  only  islands  existed,  grow  involved  in  their 
distribution,  and  widely-different  in  different  parts  of  the 
continent.  The  quantities  of  rain  which  they  discharge  and 
of  moisture  which  they  absorb,  vary  everywhere  according 
to  the  proximity  to  the  sea  and  to  surfaces  of  land  having 
special  characters. 

Other  complications  result  from  variations  of  height  above 


504  THE  EVOLUTION  OF  LIFE. 

the  sea:  elevation  producing  a  decrease  of  heat  and  conse- 
quently an  increase  in  the  precipitation  of  water — a  precipit- 
ation which  takes  the  shape  of  snow  where  the  elevation  is 
very  great,  and  of  rain  where  it  is  not  so  great.  The  gather- 
ings of  clouds  and  descents  of  showers  around  mountain 
tops,  are  familiar  to  every  tourist.  Inquiries  in  the  neigh- 
bouring valleys  prove  that  within  distances  of  a  mile  or  two 
the  recurring  storms  differ  in  their  frequency  and  violence. 
Nay,  even  a  few  yards  off,  the  meteorological  conditions  vary 
in  such  regions:  as  witness  the  way  in  which  the  condensing 
vapour  keeps  eddying  round  on  one  side  of  some  high  crag, 
while  the  other  side  is  clear;  or  the  way  in  which  the  snow- 
line  runs  irregularly  to  different  heights,  in  all  the  hollows 
and  ravines  of  each  mountain  side. 

As  climatic  variations  thus  geologically  produced,  are 
compounded  with  those  which  result  from  slow  astronomical 
changes;  and  as  no  correspondence  exists  between  the 
geologic  and  the  astronomic  rhythms ;  it  results  that  the  same 
plexus  of  actions  never  recurs.  Hence  the  incident  forces 
to  which  the  organisms  of  every  locality  are  exposed  by  atmos- 
pheric agencies,  are  ever  passing  into  unparalleled  combina- 
tions; and  these  are  on  the  average  ever  becoming  more 
complex. 

§  151.  Besides  changes  in  the  incidence  of  inorganic 
forces,  there  are  equally  continuous,  and  still  more  involved, 
changes  in  the  incidence  of  forces  which  organisms  exercise 
on  one  another.  As  before  pointed  out  (§105),  the  plants 
and  animals  inhabiting  each  locality  are  held  together  in  so 
entangled  a  web  of  relations,  that  any  considerable  modifica- 
tion which  one  species  undergoes,  acts  indirectly  on  many 
other  species,  and  eventually  changes,  in  some  degree,  the 
circumstances  of  nearly  all  the  rest.  If  an  increase  of  heat, 
or  modification  of  soil,  or  decrease  of  humidity,  causes  a  par- 
ticular kind  of  plant  either  to  thrive  or  to  dwindle,  an 
unfavourable  or  favourable  effect  is  wrought  on  all  such 


EXTERNAL  FACTORS.  505 

competing  kinds  of  plants  as  are  not  immediately  influenced 
in  the  same  way.  The  animals  which  eat  the  seeds  or  hrowse 
on  the  leaves,  either  of  the  plant  primarily  affected  or  those  of 
its  competitors,  are  severally  altered  in  their  states  of  nutri- 
tion and  in  their  numbers;  and  this  change  presently  tells 
on  various  predatory  animals  and  parasites.  And  since  each 
of  these  secondary  and  tertiary  changes  becomes  itself  a  centre 
of  others,  the  increase  or  decrease  of  each  species  produces 
waves  of  influence  which  spread  and  reverberate  and  re- 
reverberate  throughout  the  whole  Flora  and  Fauna  of  the 
locality. 

More  marked  and  multiplied  still,  are  the  ultimate  effects 
of  those  causes  which  make  possible  the  colonization  of  neigh- 
bouring areas.  Each  intruding  plant  or  animal,  besides  the 
new  inorganic  conditions  to  which  it  is  subject,  is  subject  to 
organic  conditions  different  from  those  to  which  it  has  been 
accustomed.  It  has  to  compete  with  some  organisms  unlike 
those  of  its  preceding  habitat.  It  must  preserve  itself  from 
enemies  not  before  encountered.  Or  it  may  meet  with  a 
species  over  which  it  has  some  advantage  greater  than  any 
it  had  over  the  species  it  was  previously  in  contact  with. 
Even  where  migration  does  not  bring  it  face  to  face  with 
new  competitors  or  new  enemies  or  new  prey,  it  inevitably 
experiences  new  proportions  among  these.  Further,  an  ex- 
panding species  is  almost  certain  to  invade  more  than  one 
adjacent  region.  Spreading  both  north  and  south,  or  east 
and  west,  it  will  come  among  the  plants  and  animals,  here  of 
a  level  district  and  there  of  a  hilly  one — here  of  an  inland 
tract  and  there  of  a  tract  bordered  by  the  sea.  And  while 
different  groups  of  its  members  will  thus  expose  themselves 
to  the  actions  and  reactions  of  different  Floras  and  Faunas, 
these  different  Floras  and  Faunas  will  simultaneously  have 
their  organic  conditions  changed  by  the  intruders. 

This  process  becomes  gradually  more  active  and  more 
complicated.  Though,  in  particular  cases,  a  plant  or  animal 
may  fall  into  simpler  relations  with  the  living  things  around 


506  THE  EVOLUTION  OF  LIFE. 

than  those  it  was  before  placed  in,  yet  it  is  manifest  that, 
on  the  average,  the  organic  environments  of  organisms  have 
been  advancing  in  heterogeneity.  As  the  number  of  species 
with  which  each  species  is  directly  or  indirectly  implicated, 
multiplies,  each  species  is  oftener  subject  to  changes  in  the 
organic  actions  which  influence  it.  These  more  frequent 
changes  severally  grow  more  involved.  And  the  correspond- 
ing reactions  affect  larger  Floras  and  Faunas,  in  ways  increas- 
ingly complex  and  varied. 

§  152.  When  the  astronomic,  geologic,  meteorologic,  and 
organic  agencies  which  are  at  work  on  each  species  of  plant 
and  animal  are  contemplated  as  becoming  severally  more 
complicated  in  themselves,  and  as  co-operating  in  ways  that 
are  always  partially  new;  it  will  be  seen  that  throughout 
all  time  there  has  been  an  exposure  of  organisms  to  endless 
successions  of  modifying  causes  which  gradually  acquire  an 
intricacy  scarcely  conceivable.  Every  kind  of  plant  and 
animal  may  be  regarded  as  for  ever  passing  into  a  new 
environment — as  perpetually  having  its  relations  to  external 
circumstances  altered,  either  by  their  changes  with  respect 
to  it  when  it  remains  stationary,  or  by  its  changes  with  respect 
to  them  when  it  migrates,  or  by  both. 

Yet  a  further  cause  of  progressive  alteration  and  compli- 
cation in  the  incident  forces,  exists.  All  other  things  con- 
tinuing the  same,  every  additional  faculty  by  which  an 
organism  is  brought  into  relation  with  external  objects,  as 
well  as  every  improvement  in  such  faculty,  becomes  a  means 
of  subjecting  the  organism  to  a  greater  number  and  variety 
of  external  stimuli,  and  to  new  combinations  of  external 
stimuli.  So  that  each  advance  in  complexity  of  organization, 
itself  becomes  an  added  source  of  complexity  in  the  incidence 
of  external  forces. 

Once  more,  every  increase  in  the  locomotive  powers  of 
animals,  increases  both  the  multiplicity  and  the  multiformity 
of  the  actions  of  things  upon  them,  and  of  their  reactions 


EXTERNAL  FACTORS.  507 

upon  things.  Doubling  a  creature's  activity  quadruples  the 
area  that  comes  within  the  range  of  its  excursions;  thus 
augmenting  in  number  and  heterogeneity,  the  external 
agencies  which  act  on  it  during  any  given  interval. 

By  compounding  the  actions  of  these  several  orders  of 
factors,  there  is  produced  a  geometric  progression  of  changes, 
increasing  with  immense  rapidity.  And  there  goes  on  an 
equally  rapid  increase  in  the  frequency  with  which  the  com- 
binations of  the  actions  are  altered,  and  the  intricacies  of 
their  co-operations  enhanced. 


CHAPTEE  X. 

INTERNAL    FACTORS. 

§153.  WE  saw  at  the  outset  (§§10—16),  that  organic 
matter  is  built  up  of  molecules  so  unstable,  that  the  slightest 
variation  in  their  conditions  destroys  their  equilibrium,  and 
causes  them  either  to  assume  altered  structures  or  to  decom- 
pose. But  a  substance  which  is  beyond  all  others  changeable 
by  the  actions  and  reactions  of  the  forces  liberated  from 
instant  to  instant  within  its  own  mass,  must  be  a  substance 
which  is  beyond  all  others  changeable  by  the  forces  acting  on 
it  from  without.  If  their  composition  fits  organic  aggregates 
for  undergoing  with  special  facility  and  rapidity  those  re-dis- 
tributions of  matter  and  motion  whence  result  individual 
organization  and  life ;  then  their  composition  must  make  them 
similarly  apt  to  undergo  those  permanent  re-distributions  of 
matter  and  motion  which  are  expressed  by  changes  of  struc- 
ture, in  correspondence  with  permanent  re-distributions  of 
matter  and  motion  in  their  environments. 

In  First  Principles,,  when  considering  the  phenomena  of 
Evolution  at  large,  the  leading  characters  and  causes  of  those 
changes  which  constitute  organic  evolution  were  briefly  traced. 
Under  each  of  the  derivative  laws  of  force  to  which  the 
passage  from  an  incoherent,  indefinite  homogeneity  to  a 
coherent,  definite  heterogeneity,  conforms,  were  given  illustra- 
tions drawn  from  the  metamorphoses  of  living  bodies.  Here 
508 


INTERNAL  FACTORS.  509 

it  will  be  needful  to  contemplate  the  several  resulting  pro- 
cesses as  going  on  at  once,  in  both  individuals  and  species. 

§  154.  Our  postulate  being  that  organic  evolution  in  gen- 
eral commenced  with  homogeneous  organic  matter,  we  have 
first  to  remember  that  the  state  of  homogeneity  is  an  un- 
stable state  (First  Principles,  §149).  In  any  aggregate 
"  the  relations  of  outside  and  inside,  and  of  comparative 
nearness  to  neighbouring  sources  of  influence,  imply  the  re- 
ception of  influences  that  are  unlike  in  quantity,  or  quality, 
or  both;  and  it  follows  that  unlike  changes  will  be  produced 
in  the  parts  thus  dissimilarly  acted  upon."  Further,  "  if 
any  given  whole,  instead  of  being  absolutely  uniform  through- 
out, consists  of  parts  distinguishable  from  one  another — if 
each  of  these  parts,  while  somewhat  unlike  other  parts,  is 
uniform  within  itself;  then,  each  of  them  being  in  unstable 
equilibrium,  it  follows  that  while  the  changes  set  up  within 
it  must  render  it  multiform,  they  must  at  the  same  time 
render  the  whole  more  multiform  than  before ; "  and  hence, 
"  whether  that  state  with  which  we  commence  be  or  be  not 
one  of  perfect  homogeneity,  the  process  must  equally  be 
towards  a  relative  heterogeneity."  This  loss  of 

homogeneity  which  the  special  instability  of  organic  aggre- 
gates fits  them  to  display  more  promptly  and  variously  than 
any  other  aggregates,  must  be  shown  in  more  numerous  ways 
in  proportion  as  the  incident  forces  are  more  numerous. 
Every  differentiation  of  structure  being  a  result  of  some 
difference  in  the  relations  of  the  parts  to  the  agencies  acting 
on  them,  it  follows  that  the  more  multiplied  and  more  unlike 
the  agencies,  the  more  varied  must  be  the  differentiations 
wrought.  Hence  the  change  from  a  state  of  homogeneity  to 
a  state  of  heterogeneity,  will  be  marked  in  proportion  as  the 
environing  actions  to  which  the  organism  is  exposed  are 
complex.  This  transition  from  a  uniform  to  a  mul- 

tiform state,  must  continue  through  successive  'Individuals. 
Given  a  series  of  organisms,  each  of  which  is  developed  from 


510  THE  EVOLUTION  OF  LIFE. 

a  portion  of  a  preceding  organism,  and  the  question  is  whether, 
after  exposure  of  the  series  for  a  million  years  to  changed  in- 
cident forces,  one  of  its  members  will  be  the  same  as  though 
the  incident  forces  had  only  just  changed.  To  say  that  it  will, 
is  implicitly  to  deny  the  persistence  of  force.  In  relation  to 
any  cause  of  divergence,  the  whole  series  of  such  organisms 
may  be  considered  as  fused  together  into  a  continuously- 
existing  organism ;  and  when  so  considered,  it  becomes  mani- 
fest that  a  continuously-acting  cause  will  go  on  working  a 
continuously-increasing  effect,  until  some  counteracting  cause 
prevents  any  further  effect. 

But  now  if  any  primordial  organic  aggregate  must,  in  it- 
self and  through  its  descendants,  gravitate  from  uniformity 
to  multiformity,  in  obedience  to  the  more  or  less  multiform 
forces  acting  on  it;  what  must  happen  if  these  multiform 
forces  are  themselves  undergoing  slow  variations  and  compli- 
cations? Clearly  the  process,  ever-advancing  towards  a  tem- 
porary limit  but  ever  having  its  limit  removed,  must  go  on 
unceasingly.  On  those  structural  changes  wrought  in  the 
once  homogeneous  aggregate  by  an  original  set  of  incident 
forces,  will  be  superposed  further  changes  wrought  by  a  modi- 
fied set  of  incident  forces;  and  so  on  throughout  all  time. 
Omitting  for  the  present  those  circumstances  which  check 
and  qualify  its  consequences,  the  instability  of  the  homo- 
geneous must  be  recognized  as  an  ever-acting  cause  of  organic 
evolution,  as  of  all  other  evolution. 

While  it  follows  that  every  organism,  considered  as  an  in- 
dividual and  as  one  of  a  series,  tends  thus  to  pass  into  a  more 
heterogeneous  state;  it  also  follows  that  every  species,  con- 
sidered as  an  aggregate  of  individuals,  tends  to  do  the  like. 
Throughout  the  area  it  inhabits,  the  conditions  can  never  be 
absolutely  uniform:  its  members  must,  in  different  parts  of 
the  area,  be  exposed  to  different  sets  of  incident  forces.  Still 
more  decided  must  this  difference  of  exposure  be  when 
its  members  spread  into  other  habitats.  Those  expansive 
and  repressive  energies  which  set  to  each  species  a  limit  that 


INTERNAL  FACTORS.  511 

perpetually  oscillates  from  side  to  side  of  a  certain  mean,  are, 
as  we  lately  saw,  frequently  changed  by  new  combinations  of 
the  external  factors — astronomic,  geologic,  meteorologic,  and 
organic.  Hence  there  from  time  to  time  arise  lines  of  di- 
minished resistance,  along  which  the  species  flows  into  new 
localities.  Such  portions  of  the  species  as  thus  migrate,  are 
subject  to  circumstances  unlike  its  previous  average  circum- 
stances. And  from  multiformity  of  the  circumstances,  must 
come  multiformity  of  the  species. 

Thus  the  law  of  the  instability  of  the  homogeneous  has 
here  a  three-fold  corollary.  As  interpreted  in  connexion  with 
the  ever-progressing,  ever-complicating  changes  in  external 
factors,  it  involves  the  conclusion  that  there  is  a  prevailing 
tendency  towards  greater  heterogeneity  in  all  kinds  of 
organisms,  considered  both  individually  and  in  successive 
generations;  as  well  as  in  each  assemblage  of  organisms  con- 
stituting a  species ;  and,  by  consequence,  in  each  genus,  order, 
and  class. 

§  155.  When  considering  the  causes  of  evolution  in 
general,  we  further  saw  (First  Principles,  §  156),  that  the 
multiplication  of  effects  aids  continually  to  increase  that 
heterogeneity  into  which  homogeneity  inevitably  lapses.  It 
was  pointed  out  that  since  "the  several  parts  of  an  aggre- 
gate are  differently  modified  by  any  incident  force ; "  and 
since  "  by  the  reactions  of  the  differently  modified  parts  the 
incident  force  itself  must  be  divided  into  differently  modi- 
fied parts ; "  it  follows  that  "  each  differentiated  division 
of  the  aggregate  thus  becomes  a  centre  from  which  a  differ- 
entiated division  of  the  original  force  is  again  diffused.  And 
since  unlike  forces  must  produce  unlike  results,  each  of  these 
differentiated  forces  must  produce,  throughout  the  aggregate, 
a  further  series  of  differentiations."  To  this  it  was  added 
that,  in  proportion  as  the  heterogeneity  increases,  the  compli- 
cations arising  from  this  multiplication  of  effects  grow  more 
marked;  because  the  more  strongly  contrasted  the  parts  of 


512  THE  EVOLUTION  OP  LIFE. 

an  aggregate  become,  the  more  different  must  be  their  reac- 
tions on  incident  forces,  and  the  more  unlike  must  be  the 
secondary  effects  which  these  initiate;  and  because  every 
increase  in  the  number  of  unlike  parts  adds  to  the  number 
of  such  differentiated  incident  forces,  and  such  secondary 
effects. 

How  this  multiplication  of  effects  conspires,  with  the  in- 
stability of  the  homogeneous,  to  work  an  increasing  multi- 
formity of  structure  in  an  organism,  was  shown  at  the  time; 
and  the  foregoing  pages  contain  further  incidental  illustra- 
tions. In  §  69  it  was  pointed  out  that  a  change  in  one 
function  must  produce  ever-complicating  perturbations  in 
other  functions;  and  that,  eventually,  all  parts  of  the 
organism  must  be  modified  in  their  states.  Suppose  that  the 
head  of  a  bison  becomes  much  heavier,  what  must  be  the 
indirect  results?  The  muscles  of  the  neck  are  put  to  greater 
exertions;  and  its  vertebrae  have  to  bear  additional  tensions 
and  pressures,  caused  both  by  the  increased  weight  of  the 
head,  and  by  the  stronger  contractions  of  the  muscles  that 
support  and  move  it.  These  muscles  also  affect  their  special 
attachments :  several  of  the  dorsal  spines  suffer  augmented 
strains;  and  the  vertebra?  to  which  they  are  fixed  are  more 
severely  taxed.  Further,  this  heavier  head  and  the  more 
massive  neck  it  necessitates,  require  a  stronger  fulcrum:  the 
whole  thoracic  arch,  and  the  fore-limbs  which  support  it, 
are  subject  to  greater  continuous  stress  and  more  violent 
occasional  shocks.  And  the  required  strengthening  of  the 
fore-quarters  cannot  take  place  without  the  centre  of  gravity 
being  changed,  and  the  hind  limbs  being  differently  reacted 
upon  during  locomotion.  Any  one  who  compares  the  out- 
line of  the  bison  with  that  of  its  congener,  the  ox,  will  see 
how  profoundly  a  heavier  head  affects  the  entire  osseous 
and  muscular  systems.  Besides  this  multiplica- 

tion of  mechanical  effects,  there  is  a  multiplication  of 
physiological  effects.  The  vascular  apparatus  is  modified 
throughout  its  whole  structure  by  each  considerable  modifi- 


INTERNAL  FACTORS.  513 

cation  in  the  proportions  of  the  body.  Increase  in  the  size 
of  any  organ  implies  a  quantitative,  and  often  a  qualitative, 
reaction  on  the  blood;  and  thus  alters  the  nutrition  of  all 
other  organs.  Such  physiological  correlations  are  exemplified 
in  the  many  differences  which  accompany  difference  of  sex. 
That  the  minor  sexual  peculiarities  are  brought  about  by  the 
physiological  actions  and  reactions,  is  shown  both  by  the 
fact  that  they  are  commonly  but  faintly  marked  until  the 
fundamentally  distinctive  organs  are  developed,  and  that 
when  the  development  of  these  is  prevented,  the  minor  sexual 
peculiarities  do  not  arise.  No  further  proof  is,  I 

think,  needed,  that  in  any  individual  organism  or  its  de- 
scendants, a  new  external  action  must,  besides  the  primary 
internal  change  which  it  works,  work  many  secondary 
changes,  as  well  as  tertiary,  changes  still  more  multiplied. 
That  tendency  towards  greater  heterogeneity  which  is  given 
to  an  organism  by  disturbing  its  environment,  is  helped  by 
the  tendency  which  every  modification  has  to  produce  other 
modifications — modifications  which  must  become  more  nu- 
merous in  proportion  as  the  organism  becomes  more  com- 
plex. Lastly,  among  the  indirect  and  involved  manifesta- 
tions of  this  tendency,  we  must  not  omit  the  innumerable 
small  irregularities  of  structure  which  result  from  the  cross- 
ing of  dissimilarly-modified  individuals.  It  was  shown 
(§§89,  90)  that  what  are  called  "spontaneous  variations," 
are  interpretable  as  results  of  miscellaneously  compounding 
the  changes  wrought  in  different  lines  of  ancestors  by  differ- 
ent conditions  of  life.  These  still  more  complex  and  multi- 
tudinous effects  so  produced,  are  further  illustrations  of  the 
multiplication  of  effects. 

Equally  in  the  aggregate  of  individuals  constituting  a 
species,  does  multiplication  of  effects  become  the  continual 
cause  of  increasing  multiformity.  The  lapse  of  a  species  into 
divergent  varieties,  initiates  fresh  combinations  of  forces 
tending  to  work  further  divergences.  The  new  varieties 
compete  with  the  parent  species  in  new  ways;  and  so  add 


514  THE  EVOLUTION  OF  LIFE. 

new  elements  to  its  circumstances.  They  modify  somewhat 
the  conditions  of  other  species  existing  in  their  habitat,  or 
in  the  habitat  they  have  invaded;  and  the  modifications 
wrought  in  such  other  species  become  additional  sources  of 
influence.  The  Flora  and  Fauna  of  every  region  are  united 
by  their  entangled  relations  into  a  whole,  of  which  no  part 
can  be  affected  without  affecting  the  rest.  Hence,  each  dif- 
ferentiation in  a  local  assemblage  of  species,  becomes  the 
cause  of  further  differentiations. 

§  156.  One  of  the  universal  principles  to  which  we  saw 
that  the  re-distribution  of  matter  and  motion  conforms,  is 
that  in  any  aggregate  made  up  of  mixed  units,  incident 
forces  produce  segregation — separate  unlike  units  and  bring 
together  like  units ;  and  it  was  shown  that  the  increasing  in- 
tegration and  definiteness  which  characterizes  each  part  of 
an  evolving  organic  aggregate,  as  of  every  other  aggregate, 
results  from  this  (First  Principles,  §  166).  It  remains  here 
to  say  that  while  the  actions  and  reactions  between  organ- 
isms and  their  changing  environments,  add  to  the  hetero- 
geneity of  organic  structures,  they  also  give  to  the 
heterogeneity  this  growing  distinctness.  At  first  sight  the 
reverse  might  be  inferred.  It  might  be  argued  that  any 
new  set  of  effects  wrought  in  an  organism  by  some  new  set 
of  external  forces,  must  tend  more  or  less  to  obliterate  the 
effects  previously  wrought — must  produce  confusion  or  in- 
defmiteness.  A  little  consideration,  however,  will  dissipate 
tlu's  impression. 

Doubtless  the  condition  under  which  alone  increasing  de- 
finiteness of  structure  can  be  acquired  by  any  part  of  an  or- 
ganism, either  in  an  individual  or  in  successive  generations,  is 
that  such  part  shall  be  exposed  to  some  set  of  tolerably-con- 
stant forces;  and  doubtless,  continual  change  of  circum- 
stances interferes  with  this.  But  the  interference  can  never 
be  considerable.  For  the  pre-existing  structure  of  an  organ- 
ism prevents  it  from  living  under  any  new  conditions  except 


INTERNAL  FACTORS.  515 

such  as  are  congruous  with  the  fundamental  characters  of  its 
organization — such  as  subject  its  essential  organs  to  actions 
substantially  the  same  as  before.  Great  changes  must  kill  it. 
Hence,  it  can  continuously  expose  itself  and  its  descendants, 
only  to  those  moderate  changes  which  do  not  destroy  the 
general  harmony  between  the  aggregate  of  incident  forces 
and  the  aggregate  of  its  functions.  That  is,  it  must  remain 
under  influences  calculated  to  make  greater  the  definiteness 
of  the  chief  differentiations  already  produced.  If,  for  ex- 
ample, we  set  out  with  an  animal  in  which  a  rudimentary 
vertebral  column  with  its  attached  muscular  system  has 
been  established;  it  is  clear  that  the  mechanical  arrange- 
ments have  become  thereby  so  far  determined,  that  subse- 
quent modifications  are  extremely  likely,  if  not  certain,  to 
be  consistent  with  the  production  of  movement  by  the  actions 
of  muscles  on  a  flexible  central  axis.  Hence,  there  will  con- 
tinue a  general  similarity  in  the  play  of  forces  to  which  the 
flexible  central  axis  is  subject;  and  so,  notwithstanding  the 
metamorphoses  which  the  vertebrate  type  undergoes,  there 
will  be  a  maintenance  of  conditions  favourable  to  increasing 
definiteness  and  integration  of  the  vertebral  column.  More- 
over, this  maintenance  of  such  conditions  becomes  secure  in 
proportion  as  organization  advances.  Each  further  com- 
plexity of  structure,  implying  some  further  complexity  in 
the  relations  between  an  organism  and  its  environment,  must 
tend  to  specialize  the  actions  and  reactions  between  it  and 
its  environment — must  tend  to  increase  the  stringency  with 
which  it  is  restrained  within  such  environments  as  admit  of 
those  special  actions  and  reactions  for  which  its  structure  fits 
it;  that  is,  must  further  guarantee  the  continuance  of  those 
actions  and  reactions  to  which  its  essential  organs  respond, 
and  therefore  the  continuance  of  the  segregating  process. 

How  in  each  species,  considered  as  an  aggregate  of  indi- 
viduals, there  must  arise  stronger  and  stronger  contrasts 
among  those  divergent  varieties  which  result  from  the  in- 
stability of  the  homogeneous  and  the  multiplication  of  effects, 


516  THE  EVOLUTION  OP  LIFE. 

need  only  be  briefly  indicated.  It  has  already  been  shown 
(First  Principles,  §  166),  that  in  conformity  to  the  universal 
law  that  mixed  units  are  segregated  by  like  incident  forces, 
there  are  produced  increasingly-definite  distinctions  among 
varieties,  wherever  there  occur  definitely-distinguished  sets 
of  conditions  to  which  the  varieties  are  respectively  subject. 

§  157.  Probably  in  the  minds  of  some,  the  reading  of  this 
chapter  has  been  accompanied  by  a  running  commentary,  to 
the  effect  that  the  argument  proves  too  much.  The  apparent 
implication  is,  that  the  passage  from  an  indefinite,  incoherent 
homogeneity  to  a  definite,  coherent  heterogeneity  in  organic 
aggregates,  must  have  been  going  on  universally;  whereas 
we  find  that  in  many  cases  there  has  been  persistence  with- 
out progression.  This  apparent  implication,  however,  is  not 
a  real  one. 

For  though  every  environment  on  the  Earth's  surface 
undergoes  changes;  and  though  usually  the  organisms  which 
each  environment  contains,  cannot  escape  certain  resulting 
new  influences;  yet  occasionally  such  new  influences  are 
escaped,  by  the  survival  of  species  in  the  unchanged  parts  of 
their  habitats,  or  by  their  spread  into  neighbouring  habitats 
which  the  change  has  rendered  like  their  original  habitats,  or 
by  both.  Any  alteration  in  the  temperature  of  a  climate  or 
its  degree  of  humidity,  is  unlikely  to  affect  simultaneously 
the  whole  area  occupied  by  a  species;  and  further,  it  can 
scarcely  fail  to  happen  that  the  addition  or  subtraction  of 
heat  or  moisture,  will  give  to  a  part  of  some  adjacent  area,  a 
climate  like  that  to  which  the  species  has  been  habituated. 
If,  again,  the  circumstances  of  a  species  are  modified  by  the 
intrusion  of  some  foreign  kind  of  plant  or  animal,  it  follows 
that  since  the  intruders  will  probably  not  spread  throughout 
its  whole  habitat,  the  species  will,  in  one  or  more  localities, 
remain  unaffected  by  them.  Especially  among  marine  crea- 
tures, must  there  frequently  occur  cases  in  which  modifying 
causes  are  continually  eluded.  Comparatively  uniform  as 


INTERNAL  FACTORS.  517 

are  the  physical  conditions  to  which  the  sea  exposes  its  in- 
habitants, it  becomes  possible  for  such  of  them  as  live  on 
widely-diffused  food,  to  be  widely  distributed;  and  wide  dis- 
tribution generally  prevents  the  members  of  a  species  from 
being  all  subject  to  the  same  cause.  Our  commonest  cirr- 
iped,  for  instance,  subsisting  on  minute  creatures  every- 
where dispersed  through  the  water;  needing  only  to  have 
some  firm  surface  on  which  to  build  up  its  shell;  and  in 
scarcely  any  danger  from  surrounding  animals;  is  able  to 
exist  on  shores  so  widely  remote  from  one  another,  that 
nearly  every  change  in  the  incident  forces  must  fall  within 
narrower  areas  than  that  which  the  species  occupies.  Nearly 
always,  therefore,  a  portion  of  the  species  will  survive  un- 
modified. Its  easily-transported  germs  will  take  possession 
of  such  new  habitats  as  have  been  rendered  fitter  by  the 
change  that  has  unfitted  some  parts  of  its  original  habitat. 
Hence,  on  successive  occasions,  while  some  parts  of  the 
species  are  slightly  transformed,  another  part  may  continu- 
ally escape  transformation  by  migrating  hither  and  thither, 
where  the  simple  conditions  needed  for  its  existence  recur  in 
nearly  the  same  combinations  as  before.  And  it  will  so 
become  possible  for  it  to  survive,  with  insignificant  structural 
changes,  throughout  long  geologic  periods. 

§  158.  The  results  to  which  we  find  ourselves  led,  are 
these. 

In  subordination  to  the  different  amounts  and  kinds  of 
forces  to  which  its  different  parts  are  exposed,  every  indi- 
vidual organic  aggregate,  like  all  other  aggregates,  tends  to 
pass  from  its  original  indistinct  simplicity  towards  a  more 
distinct  complexity.  Unless  we  deny  the  persistence  of 
force,  we  must  admit  that  the  lapse  of  an  organism's  struc- 
ture from  an  indefinitely  homogeneous  to  a  definitely  hetero- 
geneous state,  must  be  cumulative  in  successive  generations, 
if  the  forces  causing  it  continue  to  act.  And  for  the  like 
reasons,  the  increasing  assemblage  of  individuals  arising  froiji 
34 


518  THE  EVOLUTION  OP  LIFE. 

a  common  stock,  is  also  liable  to  lose  its  original  uniformity ; 
and,  in  successive  generations,  to  grow  more  pronounced  in 
its  multiformity. 

These  changes,  which  would  go  to  but  a  comparatively 
small  extent  were  organisms  exposed  to  constant  external 
conditions,  are  kept  up  by  the  continual  changes  in  external 
conditions,  produced  by  astronomic,  geologic,  meteorologic, 
and  organic  agencies:  the  average  result  being,  that  on 
previous  complications  wrought  by  previous  incident  forces, 
new  complications  are  continually  superposed  by  new  inci- 
dent forces.  And  hence  simultaneously  arises  increasing 
heterogeneity  in  the  structures  of  individuals,  in  the  struc- 
tures of  species,  and  in  the  structures  of  the  Earth's  Flora 
and  Fauna. 

But  while,  in  very  many  or  in  most  cases,  the  ever- 
changing  incidence  of  forces  is  ever  adding  to  the  complexity 
of  organisms,  and  to  the  complexity  of  the  organic  world  as 
a  whole ;  it  does  this  only  where  its  action  cannot  be  eluded. 
And  since,  by  migration,  it  is  possible  for  a  species  to  keep 
itself  under  conditions  that  are  tolerably  constant,  there 
must  be  a  proportion  of  cases  in  which  greater  heterogeneity 
of  structure  is  not  to  be  expected. 

To  show,  however,  that  there  must  arise  a  certain  average 
tendency  to  the  production  of  greater  heterogeneity  is  not 
sufficient.  Aggregates  might  be  rendered  more  heterogeneous 
by  changing  incident  forces,  without  having  given  to  them 
that  kind  of  heterogeneity  required  for  carrying  on  life. 
Hence  it  remains  now  to  inquire  how  the  production  and 
maintenance  of  this  kind  of  heterogeneity  is  insured. 


CHAPTER    XL 

DIRECT    EQUILIBRATION". 

§  159.  EVERY  change  is  towards  a  balance  of  forces;  and 
of  necessity  can  never  cease  until  a  balance  of  forces  is 
reached.  When  treating  of  equilibration  under  its  general 
aspects  (First  Principles,  Part  II.,  Chap,  xxii.),  we  saw  that 
every  aggregate  having  compound  movements  tends  continu- 
ally towards  a  moving  equilibrium;  since  any  unequilibrated 
force  to  which  such  an  aggregate  is  subject,  if  not  of  a  kind 
to  overthrow  it  altogether,  must  continue  modifying  its  state 
until  an  equilibrium  is  brought  about.  And  we  saw  that  the 
structure  simultaneously  reached  must  be  "  one  presenting 
an  arrangement  of  forces  that  counterbalance  all  the  forces 
to  which  the  aggregate  is  subject ; "  since,  "  so  long  as  there 
remains  a  residual  force  in  any  direction — be  it  excess  of 
a  force  exercised  by  an  aggregate  on  its  environment,  or  of 
a  force  exercised  by  its  environment  on  the  aggregate,  equi- 
librium does  not  exist;  and  therefore  the  re-distribution  of 
matter  must  continue." 

It  is  essential  that  this  truth  should  here  be  fully  compre- 
hended; and  to  the  end  of  insuring  clear  comprehension  of 
it,  some  re-illustration  is  desirable.  The  case  of  the  Solar 
System  will  best  serve  our  purpose.  An  assemblage  of  bodies, 
each  of  which  has  its  simple  and  compound  motions  that 
severally  alternate  between  two  extremes,  and  the  whole  of 
which  has  its  involved  perturbations,  that  now  increase 

519 


520  THE  EVOLUTION  OF  LIFE. 

and  now  decrease,  is  here  presented  to  us.  Suppose  a  new 
factor  were  brought  to  bear  on  this  moving  equilibrium — say 
by  the  arrival  of  some  wandering  mass,  or  by  an  additional 
momentum  given  to  one  of  the  existing  masses — what  would 
be  the  result?  If  the  strange  body  or  the  extra  energy  were 
very  large,  it  might  so  derange  the  entire  system  as  to  cause 
its  collapse.  But  what  if  the  incident  energy,  falling  on  the 
system  from  without,  proved  insufficient  to  overthrow  it? 
There  would  then  arise  a  set  of  perturbations  which  would, 
in  the  course  of  an  enormous  period,  slowly  work  round  into 
a  modified  moving  equilibrium.  The  effects  primarily  im- 
pressed on  the  adjacent  masses,  and  in  a  smaller  degree  on 
the  remoter  masses,  would  presently  become  complicated 
with  the  secondary  effects  impressed  by  the  disturbed  masses 
on  one  another;  and  these  again  with  tertiary  effects.  Waves 
of  perturbation  would  continue  to  be  propagated  throughout 
the  entire  system;  until,  around  a  new  jcentre  of  gravity, 
there  had  been  established  a  set  of  planetary  motions  different 
from  the  preceding  ones.  The  new  energy  must  gradually  be 
used  up  in  overcoming  the  energies  resisting  the  divergence 
it  generates;  which  antagonizing  energies,  when  no  longer 
opposed,  set  up  a  counter-action,  ending  in  a  compensating 
divergence  in  the  opposite  direction,  followed  by  a  re-com- 
pensating divergence,  and  so  on.  Now  though  instead 
of  being,  like  the  Solar  System,  in  a  state  of  independent 
moving  equilibrium,  an  organism  is  in  a  state  of  dependent 
moving  equilibrium  (First  Principles,  §  170) ;  yet  this  does 
not  prevent  the  manifestation  of  the  same  law.  Every 
animal  daily  obtains  from  without,  a  supply  of  energy  to 
replace  the  energy  it  expends ;  but  this  continual  giving  to  its 
parts  a  new  momentum,  to  make  up  for  the  momentum  con- 
tinually lost,  does  not  interfere  with  the  carrying  on  of 
actions  and  reactions  like  those  just  described.  Here,  as 
before,  we  have  a  definitely-arranged  aggregate  of  parts, 
called  organs,  having  their  definitely-established  actions  and 
reactions,  called  functions.  These  rhythmical  actions  or 


DIRECT  EQUILIBRATION.  521 

functions,  and  the  various  compound  rhythms  resulting  from 
their  combinations,  are  so  adjusted  as  to  balance  the  actions 
to  which  the  organism  is  subject:  there  is  a  constant  or 
periodic  genesis  of  energies  which,  in  their  kinds,  amounts, 
and  directions,  suffice  to  antagonize  the  energies  the  organism 
has  constantly  or  periodically  to  bear.  If,  then,  there  exists 
this  moving  equilibrium  among  a  set  of  internal  actions, 
exposed  to  a  set  of  external  actions,  what  must  result  if  any 
of  the  external  actions  are  changed?  Of  course  there  is  no 
longer  an  equilibrium.  Some  energy  which  the  organism 
habitually  generates,  is  too  great  or  too  small  to  balance  some 
incident  energy;  and  there  arises  a  residual  energy  exerted 
by  the  environment  on  the  organism,  or  by  the  organism  on 
the  environment.  This  residual  or  unbalanced  energy,  of 
necessity  expends  itself  in  producing  some  change  of  state  in 
the  organism.  Acting  directly  on  some  organ  and  modify- 
ing its  function,  it  indirectly  modifies  dependent  functions 
and  remotely  influences  all  the  functions.  As  we  have 
already  seen  (§§  68,  69),  if  this  new  energy  is  permanent,  its 
effects  must  be  gradually  diffused  throughout  the  entire  sys- 
tem; until  it  has  come  to  be  equilibrated  in  producing  those 
structural  rearrangements  whence  result  a  counter-balancing 
energy. 

The  bearing  of  this  general  truth  on  the  question  we  are 
now  dealing  with  is  obvious.  Those  modifications  upon 
modifications,  which  the  unceasing  mutations  of  their  en- 
vironments have  been  all  along  generating  in  organisms, 
have  been  in  each  case  modifications  involved  by  the  estab- 
lishment of  a  new  balance  with  the  new  combination  of 
actions.  In  every  species  throughout  all  geologic  time, 
there  has  been  perpetually  going  on  a  rectification  of  the 
equilibrium,  which  has  been  perpetually  disturbed  by  the 
alteration  of  its  circumstances;  and  every  further  hetero- 
geneity has  been  the  addition  of  a  structural  change  entailed 
by  a  new  equilibration,  J;o  the  structural  changes  entailed  by 
previous  equilibrations.  There  can  be  no  other  ultimate  in- 


522  THE  EVOLUTION  OF  LIFE. 

terpretation  of  the  matter,  since  change  can  have  no  other 
goal. 

This  equilibration  between  the  functions  of  an  organism 
and  the  actions  in  its  environment,  may  be  either  direct  or 
indirect.  The  new  incident  force  may  either  immediately 
call  forth  some  counteracting  force,  and  its  concomitant 
structural  change;  or  it  may  be  eventually  balanced  by  some 
otherwise-produced  change  of  function  and  structure.  These 
two  processes  of  equilibration  are  quite  distinct,  and  must  be 
separately  dealt  with.  We  will  devote  this  chapter  to  the 
first  of  them. 

§  160.  Direct  equilibration  is  that  process  currently 
known  as  adaptation.  We  have  already  seen  (Part  II.,  Chap, 
v. ) ,  that  individual  organisms  become  modified  when  placed  in 
new  conditions  of  life — so  modified  as  to  re-adjust  the  powers 
to  the  requirements;  and  though  there  is  great  difficulty  in 
disentangling  the  evidence,  we  found  reason  for  thinking 
(§82)  that  structural  changes  thus  caused  by  functional 
changes  are  inherited.  In  the  last  chapter,  it  was  argued 
that  if,  instead  of  the  succession  of  individuals  constituting  a 
species,  there  were  a  continuously-existing  individual,  any 
functional  and  structural  divergence  produced  by  a  new  inci- 
dent action,  would  increase  until  the  new  incident  action  was 
counterpoised;  and  that  the  replacing  of  a  continuously- 
existing  individual  by  a  succession  of  individuals,  each  formed 
out  of  the  modified  substance  of  its  predecessor,  will  not  pre- 
vent the  like  effect  from  being  produced.  Here  we  further 
find  that  this  limit  towards  which  any  such  organic  change 
advances,  in  the  species  as  in  the  individual,  is  a  new  moving 
equilibrium  adjusted  to  the  new  arrangement  of  external 
forces. 

But  now  what  are  the  conditions  under  which  alone,  direct 
equilibration  can  occur?  Are  all  the  modifications  that  serve 
to  re-fit  organisms  to  their  environments,  directly  adapt  !v? 
modifications?  And  if  otherwise,  which  are  the  directly 


DIRECT  EQUILIBRATION.  523 

adaptive  and  which  are  not?      How  are  we  to  distinguish 
between  them? 

There  can  be  no  direct  equilibration  with  an  external 
agency  which,  if  it  acts  at  all,  acts  fatally;  since  the  organism 
to  be  adapted  disappears.  Conversely,  some  inaccessible 
benefit  which  a  small  modification  in  the  organism  would 
make  accessible,  cannot  by  its  action  tend  to  produce  this 
modification:  the  modification  and  the  benefit  do  not  stand 
in  dynamic  relation.  The  only  new  incident  forces  which 
can  work  the  changes  of  function  and  structure  required  to 
bring  any  animal  or  plant  into  equilibrium  with  them,  are 
such  incident  forces  as  operate  on  this  animal  or  plant, 
either  continuously  or  frequently.  They  must  be  capable  of 
appreciably  changing  that  set  of  complex  rhythmical  actions 
and  reactions  constituting  the  life  of  the  organism;  and  yet 
must  not  usually  produce  perturbations  that  are  fatal.  Let 
us  see  what  are  the  limits  to  direct  equilibration  hence 
arising. 

§  161.  In  plants,  organs  engaged  in  nutrition,  and  exposed 
to  variations  in  the  amounts  and  proportions  of  matters  and 
forces  utilized  in  nutrition,  may  be  expected  to  undergo  cor- 
responding variations.  We  find  evidence  that  they  do  this. 
The  "  changes  of  habit "  which  are  common  in  plants,  when 
taken  to  places  unlike  in  climate  or  soil  to  those  before  in- 
habited by  them,  are  changes  of  parts  in  which  the  modified 
external  actions  directly  produce  modified  internal  actions. 
The  characters  of  the  stem  and  shoots  as  woody  or  succulent, 
erect  or  procumbent;  of  the  leaves  in  respect  of  their  sizes, 
thicknesses,  and  textures;  of  the  roots  in  their  degrees  of 
development  and  modes  of  growth;  are  obviously  in  imme- 
diate relation  to  the  characters  of  the  environment.  A  per- 
manent difference  in  the  quantity  of  light  or  heat  affects,  day 
after  day,  the  processes  going  on  in  the  leaves.  Habitual  rain 
or  drought  alters  all  the  assimilative  actions,  and  appre- 
ciably influences  the  organs  that  carry  them  on.  Some  par- 


524  THE  EVOLUTION  OF  LIFE. 

ticular  substance,  by  its  presence  in  the  soil,  gives  new  quali- 
ties to  some  of  the  tissues;  causing  greater  rigidity  or  flexi- 
bility, and  so  affecting  the  general  aspect.  Here  then  we 
have  changes  towards  modified  sets  of  functions  and  struc- 
tures, in  equilibrium  with  modified  sets  of  external  forces. 

But  now  let  us  turn  to  other  classes  of  organs  possessed  by 
plants — organs  which  are  not  at  once  affected  in  their  actions 
by  variations  of  incident  forces.  Take  first  the  organs  of 
defence.  Many  plants  are  shielded  against  animals  that 
would  else  devour  them,  by  formidable  thorns;  and  others, 
like  the  nettle,  by  stinging  hairs.  These  must  be  counted 
among  the  appliances  by  which  equilibrium  is  maintained 
between  the  actions  in  the  organism  and  the  actions  in  its 
environment;  seeing  that  were  these  defences  absent,  the 
destruction  by  herbivorous  animals  would  be  so  much  in- 
creased, that  the  number  of  young  plants  annually  produced 
would  not  suffice,  as  it  now  does,  to  balance  the  mortality, 
and  the  species  would  disappear.  But  these  defensive 
appliances,  though  they  aid  in  maintaining  the  balance 
between  inner  and  outer  actions,  cannot  have  been  directly 
called  forth  by  the  outer  actions  which  they  serve  to  neutra- 
lize; for  these  outer  actions  do  not  continuously  affect  the 
functions  of  the  plant  even  in  a  general  way,  still  less  in  the 
special  way  required.  Suppose  a  species  of  nettle  bare  of 
poison-hairs,  to  be  habitually  eaten  by  some  mammal  in- 
truding on  its  habitat.  The  actions  of  this  mammal  would 
have  no  direct  tendency  to  develop  poison-hairs  in  the 
plant;  since  the  individuals  devoured  could  not  bequeath 
changes  of  structure,  even  were  the  actions  of  a  kind  to  pro- 
duce fit  ones;  and  since  the  individuals  which  perpetuated 
themselves  would  be  those  on  which  the  new  incident  force 
had  not  fallen.  Organs  of  another  class,  similarly  cir- 

cumstanced, are  those  of  reproduction.  Like  the  organs  of 
defence  these  are  not,  during  the  life  of  the  individual  plant, 
variably  exercised  by  variable  external  actions;  and  there- 
fore do  not  fulfil  those  conditions  under  which  structural 


DIRECT  EQUILIBRATION.  525 

changes  may  be  directly  caused  by  changes  in  the  environ- 
ment. The  generative  apparatus  contained  in  every  flower 
acts  only  once  during  its  existence;  and  even  then,  the  parts 
subserve  their  ends  in  a  passive  rather  than  an  active  way. 
Functionally-produced  modifications  are  therefore  out  of  the 
question.  If  a  plant's  anthers  are  so  placed  that  the  insect 
which  most  commonly  frequents  its  flowers,  must  come  in 
contact  with  the  pollen,  and  fertilize  with  it  other  flowers  of 
the  same  species;  and  if  this  insect,  dwindling  away  or  dis- 
appearing from  the  locality,  leaves  behind  no  insects  having 
such  shapes  and  habits  as  cause  them  to  do  the  same  thing 
efficiently,  but  only  some  which  do  it  inefficiently;  it  is 
clear  that  this  change  of  its  conditions  has  no  immediate 
tendency  to  work  in  the  plant  any  such  structural  change 
as  shall  bring  about  a  new  balance  with  its  conditions.  For 
the  anthers,  which,  even  when  they  discharge  their  functions, 
do  it  simply  by  standing  in  the  way  of  the  insect,  are,  under 
the  supposed  circumstances,  left  untouched  by  the  insect; 
and  this  remaining  untouched  cannot  have  the  effect  of  so 
modifying  the  stamens  as  to  bring  the  anthers  into  a  position 
to  be  touched  by  some  other  insect.  Only  those  individuals 
whose  parts  of  fructification  so  far  differed  from  the  average 
form  that  some  other  insect  could  serve  them  as  pollen- 
carrier,  would  have  good  chances  of  perpetuating  themselves. 
And  on  their  progeny,  inheriting  the  deviation,  there  would 
act  no  external  force  directly  tending  to  make  the  deviation 
greater ;  since  the  new  circumstances  to  which  re-adaptation  is 
required,  are  such  as  do  not  in  the  least  alter  the  equilibrium 
of  functions  constituting  the  life  of  the  individual  plant. 

§  162.  Among  animals,  adaptation  by  direct  equilibration 
is  similarly  traceable  wherever,  during  the  life  of  the  indi- 
vidual, an  external  change  generates  some  constant  or  re- 
peated change  of  function.  This  is  conspicuously  the  case 
with  such  parts  of  an  animal  as  are  immediately  exposed  to 
diffused  influences,  like  those  of  climate,  and  with  such  parts 


526  THE  EVOLUTION  OP  LIFE. 

of  an  animal  as  are  occupied  in  its  mechanical  actions  on  the 
environment.  Of  the  one  class  of  cases,  the  darkening  of 
the  skin  which  follows  exposure  to  one  or  other  extreme  of 
temperature,  may  be  taken  as  an  instance;  and  with  the 
other  class  of  cases  we  are  made  familiar  by  the  increase  and 
decrease  which  use  and  disuse  cause  in  the  organs  of  motion. 
It  is  needless  here  to  exemplify  these:  they  were  treated  of 
in  the  Second  Part  of  this  work. 

But  in  animals,  as  in  plants,  there  are  many  indispensable 
offices  fulfilled  by  parts  between  which  and  the  external  con- 
ditions they  respond  to,  there  is  no  such  action  and  reaction 
as  can  directly  produce  an  equilibrium.  This  is  especially 
manifest  with  dermal  appendages.  Some  ground  exists  for 
the  conclusion  that  the  greater  or  less  development  of  hairs, 
is  in  part  immediately  due  to  increase  or  decrease  of  demand 
on  the  passive  function,  as  forming  a  non-conducting  coat; 
but  be  this  as  it  may,  it  is  impossible  that  there  can  exist 
any  such  cause  for  those  immense  developments  of  hairs  which 
we  see  in  the  quills  of  the  porcupine,  or  those  complex  de- 
velopments of  them  known  as  feathers.  Such  an  enamelled 
armour  as  is  worn  by  Lcpidosteus,  is  inexplicable  as  a  direct 
result  of  any  functionally-worked  change.  For  purposes  of 
defence,  such  an  armour  is  as  needful,  or  more  needful,  for 
hosts  of  other  fishes;  and  did  it  result  from  any  direct  re- 
action of  the  organism  against  any  offensive  actions  it  was 
subject  to,  there  seems  no  reason  why  other  fishes  should  not 
have  developed  similar  protective  coverings.  Of 

sundry  reproductive  appliances  the  like  may  be  said.  The 
secretion  of  an  egg-shell  round  the  substance  of  an  egg,  in 
the  oviduct  of  a  bird,  is  quite  inexplicable  as  a  consequence 
of  some  functionally-wrought  modification  of  structure,  im- 
mediately caused  by  some  modification  of  external  con- 
ditions. The  end  fulfilled  by  the  egg-shell,  is  that  of 
protecting  the  contained  mass  against  certain  slight  pres- 
sures and  collisions,  to  which  it  is  liable  during  incubation. 
How,  by  any  process  of  direct  equilibration,  could  it  come  to 


DIRECT  EQUILIBRATION.  527 

have  the  required  thickness  ?  or,  indeed,  how  could  it  come  to 
exist  at  all?  Suppose  this  protective  envelope  to  be  too 
weak,  so  that  some  of  the  eggs  a  bird  lays  are  broken  or 
cracked.  In  the  first  place,  the  breakages  or  crackings  are 
actions  which  cannot  react  on  the  maternal  organism  in  such 
ways  as  to  cause  the  secretion  of  thicker  shells  for  the 
future:  to  suppose  that  they  can,  is  to  suppose  that  the 
bird  understands  the  cause  of  the  evil,  and  that  the  secre- 
tion of  thicker  shells  can  be  effected  by  its  will.  In  the 
second  place,  such  developing  chicks  as  are  contained  in  the 
shells  which  crack  or  break,  are  almost  certain  to  die;  and 
cannot,  therefore,  acquire  appropriately-modified  constitu- 
tions: even  supposing  any  relation  could  exist  between  the 
impression  received  and  the  change  required.  Meanwhile, 
such  eggs  as  escape  breakage  are  not  influenced  at  all  by  the 
requirement ;  and  hence,  on  the  birds  developed  from  them, 
there  cannot  have  acted  any  force  tending  to  work  the  need- 
ful adjustment  of  functions.  In  no  way,  therefore,  can  a 
direct  equilibration  between  constitution  and  conditions  be 
here  produced.  Even  in  organs  that  can  be  modified 

by  certain  incident  actions  into  correspondence  with  such  in- 
cident actions,  there  are  some  re-adjustments  which  cannot 
be  effected  by  direct  balancing.  It  is  thus  with  the  bones. 
The  majority  of  the  bones  have  to  resist  muscular  strains; 
and  variations  in  the  muscular  strains  call  forth,  by  reaction, 
variations  in  the  strengths  of  the  bones.  Here  there  is 
direct  equilibration.  But  though  the  greater  massiveness 
acquired  by  bones  subject  to  greater  strains,  may  be  ascribed 
to  counter-acting  forces  evoked  by  forces  brought  into 
action;  it  is  impossible  that  the  acquirement  of  greater 
lengths  by  bones  can  be  thus  accounted  for.  It  has  been 
supposed  that  the  elongation  of  the  metatarsals  in  wading 
birds,  has  resulted  from  direct  adaptation  to  conditions  of 
life.  To  justify  this  supposition,  however,  it  must  be  shown 
that  the  mechanical  actions  and  reactions  in  the  legs  of  a 
wading  bird,  differ  from  those  in  the  legs  of  other  birds;  and 
that  the  differential  actions  are  equilibrated  by  the  extra 


528  THE  EVOLUTION  OP  LIFE. 

lengths.  There  is  not  the  slightest  evidence  of  this.  The 
metatarsals  of  a  bird  have  to  bear  no  appreciable  strains  but 
those  due  to  the  superincumbent  weight.  Standing  in  the 
water  does  not  appreciably  alter  such  strains;  and  even  if 
it  did,  an  increase  in  the  lengths  of  these  bones  would  not 
fit  them  any  better  to  meet  the  altered  strains. 

§  163.  The  conclusion  at  which  we  arrive  is,  then,  that 
there  go  on  in  all  organisms,  certain  changes  of  function  and 
structure  that  are  directly  consequent  on  changes  in  the  inci- 
dent forces — inner  changes  by  which  the  outer  changes  are 
balanced,  and  the  equilibrium  restored.  Such  re-equi- 
librations, which  are  often  conspicuously  exhibited  in  in- 
dividuals, we  have  reason  to  believe  continue  in  successive 
generations ;  until  they  are  completed  by  the  arrival  at  struc- 
tures fitted  to  the  modified  conditions.  But,  at  the  same 
time,  we  see  that  the  modified  conditions  to  which  organ- 
isms may  be  adapted  by  direct  equilibration,  are  conditions 
of  certain  classes  only.  That  a  new  external  action  may  be 
met  by  a  new  internal  action,  it  is  needful  that  it  shall  either 
continuously  or  frequently  be  borne  by  the  individuals  of 
the  species,  without  killing  or  seriously  injuring  them;  and 
shall  act  in  such  way  as  to  affect  their  functions.  And  we 
find  that  many  of  the  environing  agencies — evil  or  good — to 
which  organisms  have  to  be  adjusted,  are  not  of  these  kinds : 
being  agencies  which  either  do'  not  immediately  affect  the 
functions  at  all,  or  else  affect  them  in  ways  that  prove  fatal. 

Hence  there  must  be  at  work  some  other  process  which 
equilibrates  the  actions  of  organisms  with  the  actions  they 
are  exposed  to.  Plants  and  animals  that  continue  to  exist, 
are  necessarily  plants  and  animals  whose  powers  balance 
the  powers  acting  on  them ;  and  as  their  environments 
change,  the  changes  which  plants  and  animals  undergo  must 
necessarily  be  changes  towards  re-establishment  of  the 
balance.  Besides  direct  equilibration,  there  must  therefore 
be  an  indirect  equilibration.  How  this  goes  on  we  have  now 
to  inquire. 


CHAPTEE  XII. 

INDIRECT    EQUILIBRATION. 

§1G4.  BESIDES  those  perturbations  produced  in  any  organ- 
ism by  special  disturbing  forces,  there  are  ever  going  on  many 
others — the  reverberating  effects  of  disturbing  forces  pre- 
viously experienced  by  the  individual,  or  by  ancestors; 
and  the  multiplied  deviations  of  function  so  caused  imply 
multiplied  deviations  of  structure.  In  §  155  there  was 
re-illustrated  the  truth,  set  forth  at  length  when  treating  of 
Adaptation  (§  69),  that  an  organism  in  a  state  of  moving 
equilibrium,  cannot  have  extra  function  thrown  on  any  organ, 
and  extra  growth  produced  in  such  organ,  without  correlative 
changes  being  entailed  throughout  all  other  functions,  and 
eventually  throughout  all  other  organs.  And  when  treating 
of  Variation  (§  90),  we  saw  that  individuals  which  have  been 
made,  by  their  different  circumstances,  to  deviate  functionally 
and  structurally  from  the  average  type  in  different  directions, 
will  bequeath  to  their  joint  offspring,  compound  perturbations 
of  function  and  compound  deviations  of  structure,  endlessly 
varied  in  their  kinds  and  amounts. 

Now  if  the  individuals  of  a  species  are  thus  necessarily 
made  unlike  in  countless  ways  and  degrees— if  in  one  in- 
dividual the  amount  of  energy  in  a  particular  direction  is 
greater  than  in  any  other  individual,  or  if  here  a  peculiar 
combination  gives  a  resulting  action  which  is  not  found  else- 
where; then,  among  all  the  individuals,  some  will  be  less 
liable  than  others  to  have  their  equilibria  overthrown  by 

529 


530  THE  EVOLUTION  OF  LIFE. 

a  particular  incident  force  previously  unexperienced.  Unless 
the  change  in  the  environment  is  so  violent  as  to  be  univer- 
sally fatal  to  the  species,  it  must  affect  more  or  less  differently 
the  slightly-different  moving  equilibria  which  the  members  of 
the  species  present.  Inevitably  some  will  be  more  stable 
than  others  when  exposed  to  this  new  or  altered  factor. 
That  is  to  say,  those  individuals  whose  functions  are  most  out 
ef  equilibrium  with  the  modified  aggregate  of  external  forces, 
will  be  those  to  die;  and  those  will  survive  whose  functions 
happen  to  be  most  nearly  in  equilibrium  with  the  modified 
aggregate  of  external  forces. 

But  this  survival  of  the  fittest  *  implies  multiplication  of 
the  fittest.  Out  of  the  fittest  thus  multiplied  there  will,  as 
before,  be  an  overthrowing  of  the  moving  equilibrium  wher- 
ever it  presents  the  least  opposing  force  to  the  new  incident 
force.  And  by  the  continual  destruction  of  the  individuals 
least  capable  of  maintaining  their  equilibria  in  presence  of 
this  new  incident  force,  there  must  eventually  be  reached  an 
altered  type  completely  in  equilibrium  with  the  altered  con- 
ditions. 

§  165.  This  survival  of  the  fittest,  which  I  have  here 
sought  to  express  in  mechanical  terms,  is  that  which  Mr. 
Darwin  has  called  "  natural  selection,  or  the  preservation  of 

*  It  will  be  seen  that  the  argument  naturally  leads  up  to  this  expression- 
Survival  of  the  Fittest — which  was  here  used  for  the  first  time.  Two  years 
later  (July,  1865)  Mr.  A.  R.  Wallace  wrote  to  Mr.  Darwin  contending  that  it 
should  be  substituted  for  the  expression  u  Natural  Selection."  Mr.  Darwin 
demurred  to  this  proposal.  Among  reasons  for  retaining  his  own  expression 
he  said  that  I  had  myself,  in  many  cases,  preferred  it—"  continually  using  the 
words  Natural  Selection."  (Life  and  Letters,  &c.,  vol.  Ill,  pp.  45-6.)  Mr. 
Darwin  was  quite  right  in  his  statement,  but  not  right  in  the  motive  he 
ascribed  to  me.  My  reason  for  frequently  using  the  phrase  "  Natural  Selec- 
tion," after  the  date  at  which  the  phrase  "  Survival  of  the  Fittest "  was  first 
used  above,  was  that  disuse  of  Mr.  Darwin's  phrase  would  have  seemed  like 
an  endeavour  to  keep  out  of  sight  my  own  indebtedness  to  him,  and  the 
indebtedness  of  the  world  at  large.  The  implied  feeling  has  led  me  ever  since 
to  use  the  expressions  Natural  Selection  and  Survival  of  the  Fittest  with  some- 
thing like  equal  frequency. 


INDIRECT  EQUILIBRATION.  531 

favoured  races  in  the  struggle  for  life."  That  there  goes 
on  a  process  of  this  kind  throughout  the  organic  world,  Mr. 
Darwin's  great  work  on  the  Origin  of  Species  has  shown  to 
the  satisfaction  of  nearly  all  naturalists.  Indeed,  when  once 
enunciated,  the  truth  of  his  hypothesis  is  so  obvious  as 
scarcely  to  need  proof.  Though  evidence  may  be  required  to 
show  that  natural  selection  accounts  for  everything  ascribed 
to  it,  yet  no  evidence  is  required  t'o  show  that  natural  selec- 
tion has  always  been  going  on,  is  going  on  now,  and  must 
ever  continue  to  go  on.  Recognizing  this  as  an  a  priori  cer- 
tainty, let  us  contemplate  it  under  its  two  distinct  aspects. 

That  organisms  which  live,  thereby  prove  themselves  fit  for 
living,  in  so  far  as  they  have  been  tried,  while  organisms  which 
die,  thereby  prove  themselves  in  some  respects  unfitted  for 
living,  are  facts  no  less  manifest  than  is  the  fact  that  this  self- 
purification  of  a  species  must  tend  ever  to  insure  adaptation 
between  it  and  its  environment.  This  adaptation  may  be 
either  so  maintained  or  so  produced.  Doubtless  many 

who  have  looked  at  Nature  with  philosophic  eyes,  have  ob- 
served that  death  of  the  worst  and  multiplication  of  the 
best,  tends  towards  maintenance  of  a  constitution  in  harmony 
with  surrounding  circumstances.  That  the  average  vigour  of 
any  race  would  be  diminished  did  the  diseased  and  feeble 
habitually  survive  and  propagate;  and  that  the  destruction 
of  such,  through  failure  to  fulfil  some  of  the  conditions  to  life, 
leaves  behind  those  which  are  able  to  fulfil  the  conditions  to 
life,  and  thus  keeps  up  the  average  fitness  to  the  conditions 
of  life;  are  almost  self-evident  truths.  But  to  recognize 
"  Natural  Selection "  as  a  means  of  preserving  an  already- 
established  balance  between  the  powers  of  a  species  and  the 
forces  to  which  it  is  subject,  is  to  recognize  only  its  simplest 
and  most  general  mode  of  action.  It  is  the  more  special 
mode  of  action  with  which  we  are  here  concerned.  This 

more  special  mode  of  action,  Mr.  Darwin  has  been  the  first 
to  recognize  as  an  all-important  factor,  though,  besides  his 
co-discoverer  Mr.  A.  R.  Wallace,  some  others  have  perceived 


532  THE  EVOLUTION  OP  LIFE. 

that  such  a  factor  is  at  work.  To  him  we  owe  due  appreciation 
of  the  fact  that  natural  selection  is  capable  of  producing  fit- 
ness between  organisms  and  their  circumstances.  He  has 
worked  up  an  enormous  mass  of  evidence  showing  that  this 
"  preservation  of  favoured  races  in  the  struggle  for  life,"  is  an 
ever-acting  cause  of  divergence  among  organic  forms.  He  has 
traced  out  the  involved  results  of  the  process  with  marvellous 
subtlety.  He  has  shown  how  hosts  of  otherwise  inexplicable 
facts,  are  accounted  for  by  it.  In  brief,  he  has  proved  that 
the  cause  he  alleges  is  a  true  cause;  that  it  is  a  cause  which 
we  see  habitually  in  action;  and  that  the  results  to  be  in- 
ferred from  it  are  in  harmony  with  the  phenomena  which 
the  Organic  Creation  presents,  both  as  a  whole  and  in  its 
details.  Let  us  glance  at  a  few  of  the  more  important  inter- 
pretations which  the  hypothesis  furnishes. 

A  soil  possessing  some  ingredient  in  unusual  quantity, 
may  supply  to  a  plant  an  excess  of  the  matter  required  for 
certain  of  its  tissues;  and  may  cause  all  the  parts  formed  of 
such  tissues  to  be  abnormally  developed.  Suppose  that 
among  these  are  the  hairs  clothing  its  surfaces,  including 
those  which  grow  on  its  seeds.  Thus  furnished  with  some- 
what longer  fibres,  its  seeds,  when  shed,  are  carried  a  little 
further  by  the  wind  before  they  fall  to  the  ground.  The 
plants  growing  from  them,  being  rather  more  widely  dis- 
persed than  those  produced  by  other  individuals  of  the  same 
species,  will  be  less  liable  to  smother  one  another;  and  a 
greater  number  may  therefore  reach  maturity  and  fructify. 
Supposing  the  next  generation  subject  to  the  same  peculiarity 
of  nutrition,  some  of  the  seeds  borne  by  its  members  will  not 
simply  inherit  this  increased  development  of  hairs,  but  will 
carry  it  further;  and  these,  still  more  advantaged  in  the 
same  way  as  before,  will,  on  the  average,  have  still  more 
numerous  chances  of  continuing  the  race.  Thus,  by  the  sur- 
vival, generation  after  generation,  of  those  possessing  these 
longer  hairs,  and  the  inheritance  of  successive  increments  of 
growth  in  the  hairs,  there  may  result  a  seed  deviating  greatly 


INDIRECT  EQUILIBRATION.  533 

from  the  original.  Other  individuals  of  the  same  species, 
subject  to  the  different  physical  conditions  of  other  localities, 
may  develop  somewhat  thicker  or  harder  coatings  to  their 
seeds:  so  rendering  their  seeds  less  digestible  by  the  birds 
which  devour  them.  Such  thicker-coated  seeds,  by  escaping 
undigested  more  frequently  than  thinner-coated  ones,  will 
have  additional  chances  of  growing  and  leaving  offspring; 
and  this  process,  acting  in  a  cumulative  manner  season  after 
season,  will  produce  a  seed  diverging  in  another  direction 
from  the  ancestral  type.  Again,  elsewhere,  some  modification 
in  the  physiologic  actions  of  the  plant  may  lead  to  an  un- 
usual secretion  of  an  essential  oil  in  the  seeds;  rendering 
them  unpalatable  to  creatures  which  would  otherwise  feed 
on  them :  so  giving  an  advantage  to  the  variety  in  its  rate 
of  multiplication.  This  incidental  peculiarity,  proving  a 
preservative,  will,  as  before,  be  increased  by  natural  selection 
until  it  constitutes  another  divergence.  Now  in  such  cases, 
we  see  that  plants  may  become  better  adapted,  or  re-adapted, 
to  the  aggregate  of  surrounding  agencies,  not  through  any 
direct  action  of  such  agencies  on  them,  but  through  their 
indirect  action — through  the  destruction  by  them  of  the  indi- 
viduals least  congruous  with  them,  and  the  survival  of  those 
most  congruous  with  them.  All  these  slight  variations  of 
function  and  structure,  arising  among  the  members  of  a 
species,  serve  as  so  many  experiments;  the  great  majority  of 
which  fail,  but  a  few  of  which  succeed.  Just  as  each  plant 
bears  a  multitude  of  seeds,  out  of  which  some  two  or  three 
happen  to  fulfil  all  the  conditions  required  for  reaching 
maturity  and  continuing  the  race;  so  each  species  is  ever 
producing  numerous  slightly-modified  forms,  deviating  in  all 
directions  from  the  average,  out  of  which  most  fit  the  sur- 
rounding conditions  no  better  than  their  parents,  or  not  so 
well,  but  some  few  of  which  fit  the  conditions  better;  and, 
doing  so,  are  enabled  the  better  to  preserve  themselves,  and 
to  produce  offspring  similarly  capable  of  preserving  them- 
selves. Among  animals  the  like  process  results  in 
35 


534  THE  EVOLUTION  OF  LIFE. 

the  like  development  of  various  structures  which  cannot 
have  been  affected  by  the  performance  of  functions — their 
functions  being  purely  passive.  The  thick  shell  of  a  mollusk 
cannot  have  arisen  from  direct  reactions  of  the  organism 
against  the  external  actions  to  which  it  is  exposed;  but  it  is 
quite  explicable  as  an  effect  of  the  survival,  generation  after 
generation,  of  individuals  whose  thicker  coverings  protected 
them  against  enemies.  Similarly  with  such  dermal  struc- 
ture as  that  of  the  tortoise.  Though  we  have  evidence  that 
the  skin,  where  it  is  continually  exposed  to  pressure  and  fric- 
tion, may  thicken,  and  so  re-establish  the  equilibrium  by 
opposing  a  greater  inner  force  to  a  greater  outer  force;  yet 
we  have  no  evidence  that  a  coat  of  armour  like  that  of  the 
tortoise  can  be  so  produced.  Nor,  indeed,  are  the  conditions 
under  which  alone  its  production  in  such  a  manner  could  be 
accounted  for,  fulfilled;  since  the  surface  of  the  tortoise  is 
not  exposed  to  greater  pressure  and  friction  than  the  surfaces 
of  other  creatures.  This  massive  carapace,  and  the  strangely- 
adapted  osseous  frame-work  which  supports  it,  are  inexplic- 
able as  results  of  evolution,  unless  through  the  process  of 
natural  selection.  So,  too,  is  it  with  the  formation  of  odori- 
ferous glands  in  some  mammals,  or  the  growth  of  such  ex- 
crescences as  those  of  the  camel.  Thus,  in  short,  is  it  with 
all  those  organs  of  animals  which  do  not  play  active  parts. 

Besides  giving  us  explanations  of  structural  characters 
that  are  otherwise  unaccountable,  Mr.  Darwin  shows  how 
natural  selection  explains  peculiar  relations  between  indi- 
viduals in  certain  species.  Such  facts  as  the  dimorphism  of 
the  primrose  and  other  flowers,  he  proves  to  be  in  harmony 
with  his  hypothesis,  though  stumbling-blocks  to  all  other 
hypotheses.  The  various  differences  which  accompany  differ- 
ence of  sex,  sometimes  slight,  sometimes  very  great,  are 
similarly  accounted  for.  As  before  suggested  (§79),  natural 
selection  appears  capable  of  producing  and  maintaining  tke 
right  proportion  of  the  sexes  in  each  species;  and  it  requires 
but  to  contemplate  the  bearings  of  the  argument,  to  see  that 


INDIRECT  EQUILIBRATION.  535 

the  formation  of  different  sexes  may  itself  have  been  deter- 
mined in  the  same  way. 

To  convey  here  an  adequate  idea  of  Mr.  Darwin's  doctrine, 
throughout  the  immense  range  of  its  applications,  is  of  course 
impossible.  The  few  illustrations  just  given,  are  intended 
simply  to  remind  the  reader  what  Mr.  Darwin's  hypothesis 
is,  and  what  are  the  else  insoluble  problems  which  it  solves 
for  us. 

§  166.  But  now,  though  it  seems  to  me  that  we  are  thus 
supplied  with  a  key  to  phenomena  which  are  multitudinous 
and  varied  beyond  all  conception;  it  also  seems  to  me  that 
there  is  a  moiety  of  the  phenomena  which  this  key  will  not 
unlock.  Mr.  Darwin  himself  recognizes  use  and  disuse  of 
parts,  as  causes  of  modifications  in  organisms;  and  does  this, 
indeed,  to  a  greater  extent  than  do  some  who  accept  his 
general  conclusion.  But  I  conceive  that  he  does  not  recog- 
nize them  to  a  sufficient  extent.  While  he  shows  that  the 
inheritance  of  changes  of  structure  caused  by  changes  of 
function,  is  utterly  insufficient  to  explain  a  great  mass — 
probably  the  greater  mass — of  morphological  phenomena;  I 
think  he  leaves  unconsidered  a  mass  of  morphological  pheno- 
mena which  are  explicable  as  results  of  functionally-produced 
modifications,  and  are  not  explicable  as  results  of  natural 
selection. 

By  induction,  as  well  as  by  inference  from  the  hypothesis 
of  natural  selection,  we  know  that  there  exists  a  balance 
among  the  powers  of  organs  which  habitually  act  together — 
such  proportions  among  them  that  no  one  has  any  consider- 
able excess  of  efficiency.  We  see,  for  example,  that  through- 
out the  vascular  system  there  is  maintained  an  equilibrium 
of  the  component  parts:  in  some  cases,  under  continued 
excess  of  exertion,  the  heart  gives  way,  and  we  have  enlarge- 
ment; in  other  cases  the  large  arteries  give  way,  and  we 
have  aneurisms;  in  other  cases  the  minute  blood-vessels  give 
way — now  bursting,  now  becoming  chronically  congested. 


536  THE  EVOLUTION  OF  LIFE. 

That  is  to  say,  in  the  average  constitution,  no  superfluous 
strength  is  possessed  by  any  of  the  appliances  for  circulating 
the  blood.  Take,  again,  a  set  of  motor  organs.  Great  strain 
here  causes  the  fibres  of  a  muscle  to  tear..  There  the  muscle 
does  not  yield  but  the  tendon  snaps.  Elsewhere  neither 
muscle  nor  tendon  is  damaged,  but  the  bone  breaks.  Joining 
with  these  instances  the  general  fact  that,  under  the  same 
adverse  conditions,  different  individuals  show  their  slight 
differences  of  constitution  by  going  wrong  some  in  one  way 
and  some  in  another;  and  that  even  in  the  same  individual, 
similar  adverse  conditions  will  now  affect  one  viscus  and  now 
another;  it  becomes  manifest  that  though  there  cannot  be 
maintained  an  accurate  balance  among  the  powers  of  the 
organs  composing  an  organism,  yet  their  excesses  and  de- 
ficiencies of  power  are  extremely  slight.  That  they  must  be 
extremely  slight,  is,  as  before  said,  a  deduction  from  the 
hypothesis  of  natural  selection.  Mr.  Darwin  himself  argues 
"  that  natural  selection  is  continually  trying  to  economise  in 
every  part  of  the  organization.  If  under  changed  conditions 
of  life  a  structure  before  useful  becomes  less  useful,  any 
diminution,  however  slight>  in  its  development,  will  be  seized 
on  by  natural  selection,  for  it  will  profit  the  individual  not 
to  have  its  nutriment  wasted  in  building  up  an  useless  struc- 
ture." In  other  words,  if  any  muscle  has  more  fibres  than 
are  required,  or  if  a  bone  is  stronger  than  needful,  no  advant- 
age results  but  rather  a  disadvantage — a  disadvantage  which 
will  decrease  the  chances  of  survival.  Hence  it 

follows  that  among  any  organs  which  habitually  act  in  con- 
cert, an  increase  of  one  can  be  of  no  service  unless  there  is  a 
concomitant  increase  of  the  rest.  The  co-operative  parts 
must  vary  together;  otherwise  variation  will  be  detrimental. 
A  stronger  muscle  must  have  a  stronger  bone  to  resist  its 
contractions;  must  have  stronger  correlated  muscles  and 
ligaments  to  secure  the  neighbouring  articulations;  .  must 
have  larger  blood-vessels  to  bring  it  supplies;  must  have  a 
more  massive  nerve  to  transmit  stimulus,  and  some  extra 


INDIRECT  EQUILIBRATION  53Y 

development  of  a  nervous  centre  to  supply  the  extra  stimu- 
lus. The  question  arises,  then, — do  variations  of  the  appro- 
priate kinds  occur  simultaneously  in  all  these  co-operative 
parts?  Have  we  any  reason  to  think  that  the  parts  spon- 
taneously increase  or  decrease  together?  The  assumption 
that  they  do  seems  to  me  untenable;  and  its  untenability 
will,  I  think,  become  conspicuous  if  we  take  a  case,  and 
observe  how  extremely  numerous  and  involved  are  the  varia- 
tions which  must  be  supposed  to  occur  together.  In 
illustration  of  another  point,  we  have  already  considered  the 
modifications  required  to  accompany  increased  weight  of  the 
head  (§  155).  Instead  of  the  bison,  the  moose  deer,  or  the 
extinct  Irish  elk,  will  here  best  serve  our  purpose.  In  this 
last  species  the  male  has  enormously-developed  horns,  used 
for  purposes  of  offence  and  defence.  These  horns,  weighing 
upwards  of  a  hundred-weight,  are  carried  at  great  mechanical 
disadvantage :  supported  as  they  are,  along  with  the  massive 
skull  which  bears  them,  at  the  extremity  of  the  outstretched 
neck.  Further,  that  these  heavy  horns  may  be  of  use  in 
fighting,  the  supporting  bones  and  muscles  must  be  strong 
enough,  not  simply  to  carry  them,  but  to  put  them  in  motion 
with  the  rapidity  needed  for  giving  blows.  Let  us,  then,  ask 
how,  by  natural  selection,  this  complex  apparatus  of  bones 
and  muscles  can  have  been  developed,  pari  passu  with  the 
horns?  If  we  suppose  the  horns  to  have  been  originally  of 
like  size  with  those  borne  by  other  kinds  of  deer;  and  if  we 
suppose  that  in  some  individual  they  became  larger  by 
spontaneous  variation;  what  would  be  the  concomitant 
changes  required  to  render  their  greater  size  useful?  Other 
things  equal,  the  blow  given  by  a  larger  horn  would  be  a 
blow  given  by  a  heavier  mass  moving  at  a  smaller  velocity: 
the  momentum  would  be  the  same  as  before;  and  the  area 
of  contact  with  the  body  struck  being  somewhat  increased, 
while  the  velocity  was  decreased,  the  injury  done  would  be 
less.  That  horns  may  become  better  weapons,  the  whole 
apparatus  concerned  in  moving  them  must  be  so  strength-, 


538  THE  EVOLUTION  OP  LIFE. 

cned  as  to  impress  more  force  on  them,  and  to  bear  the  more 
violent  reactions  of  the  blows  given.  The  bones  of  the  skull 
on  which  the  horns  are  seated  must  be  thickened;  otherwise 
they  will  break.  The  vertebrae  of  the  neck  must  be  further 
developed;  and  unless  the  ligaments  which  hold  together 
these  vertebrae,  and  the  muscles  which  move  them,  are  also 
enlarged,  nothing  will  be  gained.  Again  the  upper  dorsal 
vertebrae  and  their  spines  must  be  strengthened,  that  they 
may  withstand  the  stronger  contractions  of  the  neck-muscles ; 
and  like  changes  must  be  made  on  the  scapular  arch.  Still 
more  must  there  be  required  a  simultaneous  development  of 
the  bones  and  muscles  of  the  fore-legs;  since  these  extra 
growths  in  the  horns,  in  the  skull,  in  the  neck,  in  the 
shoulders,  add  to  the  burden  they  have  to  bear;  and  without 
they  are  strengthened  the  creature  will  not  only  suffer  from 
loss  of  speed  but  will  fail  in  fight.  Hence,  to  make  larger 
horns  of  use,  additional  sizes  must  be  acquired  by  numerous 
bones,  muscles,  and  ligaments,  as  well  as  by  the  blood-ves- 
sels and  nerves  on  which  their  actions  depend.  On  call- 
ing to  mind  how  the  spraining  of  a  single  small  muscle  in 
the  foot  incapacitates  for  walking,  or  how  permanent  weak- 
ness in  a  knee-ligament  will  diminish  the  power  of  the  leg, 
it  will  be  seen  that  unless  all  these  many  changes  are  simul- 
taneously made,  they  may  as  well  be  none  of  them  made — 
or  rather,  they  would  better  be  none  of  them  made;  since 
the  enlargements  of  some  parts,  by  putting  greater  strains 
on  connected  parts,  would  render  them  relatively  weaker  if 
they  remained  unenlarged.  Can  we  with  any  propriety 
assume  that  these  many  enlargements  duly  proportioned  will 
be  simultaneously  effected  by  spontaneous  variations?  I 
think  not.  It  would  be  a  strong  supposition  that  the  verte- 
brae and  muscles  of  the  neck  suddenly  became  bigger  at  the 
same  time  as  the  horns.  It  would  be  a  still  stronger  sup- 
position that  the  upper  dorsal  vertebra?  not  only  at  the  same 
time  became  more  massive,  but  appropriately  altered  their 
proportions,  by  the  development  of  their  immense  neural 


INDIRECT  EQUILIBRATION.  539 

spines.  And  it  would  be  an  assumption  still  more  straining 
our  powers  of  belief,  that  along  with  heavier  horns  there 
should  spontaneously  take  place  the  required  strengthenings 
in  the  bones,  muscles,  arteries,  and  nerves  of  the  scapular 
and  the  fore-legs. 

Besides  the  multiplicity  of  directly-cooperative  organs,  the 
multiplicity  of  organs  which  do  not  cooperate,  save  in  the 
degree  implied  by  their  combination  in  the  same  organism, 
seems  to  me  a  further  hindrance  to  the  development  of 
special  structures  by  natural  selection  alone.  Where  the  life 
is  simple,  or  where  circumstances  render  some  one  function 
supremely  important,  survival  of  the  fittest  may  readily 
bring  about  the  appropriate  structural  change,  without  aid 
from  the  transmission  of  functionally-caused  modifications. 
But  in  proportion  as  the  life  grows  complex — in  proportion 
as  a  healthy  existence  cannot  be  secured  by  a  large  endow- 
ment of  some  one  power,  but  demands  many  powers;  in  the 
same  proportion  do  there  arise  obstacles  to  the  increase  of 
any  particular  power  by  "  the  preservation  of  favoured  races 
in  the  struggle  for  life."  As  fast  as  the  faculties  are  multi- 
plied, so  fast  does  it  become  possible  for  the  several  members 
of  a  species  to  have  various  kinds  of  superiorities  over  one 
another.  While  one  saves  its  life  by  higher  speed,  another 
does  the  like  by  clearer  vision,  another  by  keener  scent, 
another  by  quicker  hearing,  another  by  greater  strength, 
another  by  unusual  power  of  enduring  cold  or  hunger, 
another  by  special  sagacity,  another  by  special  timidity, 
another  by  special  courage;  and  others  by  other  bodily  and 
mental  attributes.  Conditions  being  alike,  each  of  these  life- 
saving  attributes  is  likely  to  be  transmitted  to  posterity.  But 
we  may  not  assume  that  it  will  be  increased  in  subse- 
quent generations  by  natural  selection.  Increase  of  it  can 
result  only  if  individuals  possessing  average  endowments  of 
it  are  more  frequently  killed  off  than  individuals  highly 
endowed  with  it;  and  this  can  happen  only  when  the  attri- 
bute is  one  of  greater  importance,  for  the  time  being,  than 


540  THE  EVOLUTION  OF  LIFE. 

most  of  the  other  attributes.  If  those  members  of  the 
species  which  have  but  ordinary  shares  of  it,  nevertheless 
survive  by  virtue  of  other  superiorities  which  they  severally 
possess;  then  it  is  not  easy  to  see  how  this  particular  attri- 
bute can  be  developed  by  natural  selection  in  subsequent 
generations.  The  probability  seems  rather  to  be  that,  by 
gamogenesis,  this  extra  endowment  will,  on  the  average,  be 
diminished  in  posterity — just  serving  in  the  long  run  to 
make  up  for  the  deficient  endowments  of  those  whose  special 
powers  lie  in  other  directions;  and  so  to  keep  up  the  normal 
structure  of  the  species.  As  fast  as  the  number  of  bodily 
and  mental  faculties  increases,  and  as  fast  as  maintenance  of 
life  comes  to  depend  less  on  the  amount  of  any  one  and  more 
on  the  combined  actions  of  all;  so  fast  does  the  production 
of  specialities  of  character  by  natural  selection  alone,  become 
difficult.  Particularly  does  this  seem  to  be  so  with  a  species 
so  multitudinous  in  its  powers  as  mankind;  and  above  all 
does  it  seem  to  be  so  with  such  of  the  human  powers  as  have 
but  minor  shares  in  aiding  the  struggle  for  life — the  aesthetic 
faculties,  for  example. 

It  by  no  means  follows,  however,  that  in  cases  of  this  kind, 
and  cases  of  the  preceding  kind,  natural  selection  plays  no 
part.  Wherever  it  is  not  the  chief  agent  in  working  organic 
changes,  it  is  still,  very  generally,  a  secondary  agent.  The 
survival  of  the  fittest  must  nearly  always  further  the  produc- 
tion of  modifications  which  produce  fitness,  whether  they  be 
incidental  modifications,  or  modifications  caused  by  direct 
adaptation.  Evidently,  those  individuals  whose  constitu- 
tions have  facilitated  the  production  in  them  of  any  struc- 
tural change  consequent  on  any  functional  change  demanded 
by  some  new  external  condition,  will  be  the  individuals  most 
likely  to  live  and  to  leave  descendants.  There  must  .be  a 
natural  selection  of  functionally-acquired  peculiarities,  as 
well  as  of  spontaneously-acquired  peculiarities;  and  hence 
such  structural  changes  in  a  species  as  result  from  changes  of 
habit  necessitated  by  changed  circumstances,  natural  selec- 
tion will  render  more  rapid  than  they  would  otherwise  be, 


INDIRECT  EQUILIBRATION.  541 

There  are,  however,  some  modifications  in  the  sizes  and 
forms  of  parts,  which  cannot  have  'been  aided  by  natural 
selection;  but  which  must  have  resulted  wholly  from  the 
inheritance  of  functionally-caused  alterations.  The  dwind- 
ling of  organs  of  which  the  undue  sizes  entail  no  appreciable 
evils,  furnishes  the  best  evidence  of  this.  Take,  for  an 
example,  that  diminution  of  the  jaws  and  teeth  which 
characterizes  the  civilized  races,  as  contrasted  with  the 
savage  races.*  How  can  the  civilized  races  have  been  bene- 

*  I  am  indebted  to  Mr.  [now  Sir  W.]  Flower  for  the  opportunity  of  ex- 
amining the  many  skulls  in  the  Museum  of  the  College  of  Surgeons  for  verifi- 
cation of  this.  Unfortunately  the  absence,  in  most  cases,  of  some  or  many 
teeth,  prevented  me  from  arriving  at  that  specific  result  which  would  have 
been  given  by  weighing  a  number  of  the  under  jaws  in  each  race.  Simple 
inspection,  however,  disclosed  a  sufficiently-conspicuous  difference.  The 
under  jaws  of  Australians  and  Negroes,  when  collated  with  those  of  English- 
men, were  visibly  laiger,  not  only  relatively  but  absolutely.  One  Australian 
jaw  only  seemed  about  of  the  same  size  as  an  average  English  jaw;  and 
this  (probably  the  jaw  of  a  woman),  belonging  as  it  did  to  a  smaller  skull, 
bore  a  greater  ratio  to  the  whole  body  of  which  it  formed  part,  than  did  an 
English  jaw  of  the  same  actual  size.  In  all  the  other  cases,  the  under  jaws 
of  these  inferior  races  (containing  larger  teeth  than  our  own)  were  absolutely 
more  massive  than  our  own — often  exceeding  them  in  all  dimensions ;  and 
relatively  to  their  smaller  skeletons  were  much  more  massive.  Let  me 
add  that  the  Australian  and  Negro  jaws  are  thus  strongly  contrasted,  not 
with  all  British  jaws,  but  only  with  the  jaws  of  the  civilized  British.  An 
ancient  British  skull  in  the  collection  possesses  a  jaw  almost  or  quite  as 
massive  as  those  of  the  Australian  skulls.  All  this  is  in  harmony  with  the 
alleged  relation  between  greater  size  of  jaws  and  greater  action  of  jaws, 
involved  by  the  habits  of  savages. 

[In  1891  Mr.  F.  Howard  Collins  carefully  investigated  this  matter:  meas- 
uring ten  Australian,  ten  Ancient  British,  and  ten  recent  English  skulls  in  the 
College  of  Surgeons  Museum.  The  result  proved  an  absolute  difference  of  the 
kind  above  indicated,  and  a  far  greater  relative  difference.  To  ascertain  this 
last  a  common  standard  of  comparison  was  established — an  equal  size  of  skull 
in  all  the  cases ;  and  then  when  the  relative  masses  or  cubic  sizes  of  the  jaws 
were  calculated,  the  result  which  came  out  was  this : — Australian  jaw,  1948  ; 
Ancient  British  jaw,  1135;  Recent  English  jaw,  1030.  "Hence,"  in  the 
words  of  Mr.  Collins,  "  the  mass  of  the  Recent  English  jaw  is,  roughly  speak- 
ing, half  that  of  the  Australian  relatively  to  that  of  the  skull,  and  a  ninth  less 
than  that  of  the  Ancient  British."  He  adds  verif  j  ing  evidence  from  witnesses 
who  have  no  hypothesis  to  support— members  of  the  Odontological  Society. 
The  Vice-President,  Mr.  Mummery,  remarks  of  the  Australians  that  "the 


542  THE  EVOLUTION  OP  LIFE, 

fited  in  the  struggle  for  life,  by  the  slight  decrease  in  these 
comparatively-small  bones?  No  functional  superiority  pos- 
sessed by  a  small  jaw  over  a  large  jaw  in  civilized  life,  can 
be  named  as  having  caused  the  more  frequent  survival  of 
small-jawed  individuals.  The  only  advantage  accompanying 
smallness  of  jaw,  is  the  advantage  of  economized  nutrition; 
and  this  cannot  be  great  enough  to  further  the  preservation 
of  those  distinguished  by  it.  The  decrease  of  weight  in  the 
jaw  and  co-operative  parts,  which  has  arisen  in  the  course 
of  thousands  of  years,  does  not  amount  to  more  than  a  few 
ounces.  This  decrease  has  to  be  divided  among  the  many 
generations  which  have  lived  and  died  in  the  interval.  Let 
us  admit  that  the  weight  of  these  parts  diminished  to  the 
extent  of  an  ounce  in  a  single  generation  (which  is  a  large 
admission) ;  it  still  cannot  be  contended  that  the  having  to 
carry  an  ounce  less  in  weight,  and  to  keep  in  repair  an  ounce 
less  of  tissue,  could  sensibly  affect  any  man's  fate.  And  if  it 
never  did  this — nay,  if  it  did  not  cause  a  frequent  survival  of 
small-jawed  individuals  where  large-jawed  individuals  died; 
natural  selection  could  neither  cause  nor  aid  diminution  of 
the  jaw  and  its  appendages.  Here,  therefore,  the  decreased 
action  which  has  accompanied  the  growth  of  civilized  habits 
(the  use  of  tools  and  the  disuse  of  coarse  food),  must  have 
been  the  sole  cause  at  work.  Through  direct  equilibration, 
diminished  external  stress  on  these  parts  has  resulted  in 
diminution  of  the  internal  forces  by  which  this  stress  is  met. 
From  generation  to  generation,  this  lessening  of  the  parts 
consequent  on  functional  decline  has  been  inherited.  And 
since  the  survival  of  individuals  must  always  have  been 
determined  by  more  important  structural  traits,  this  trait 
can  have  neither  been  facilitated  nor  retarded  by  natural 
selection. 

§167.  Returning  from  these  extensive  classes  of  facts  for 

jaw-bones  are  powerfully  developed,  and  large  in  proportion  to  the  cra- 
nium."] 


INDIRECT  EQUILIBRATION.  543 

which  Mr.  Darwin's  hypothesis  does  not  account,  to  the  still 
more  extensive  classes  of  facts  for  which  it  does  account, 
and  which  are  unaccountable  on  any  other  hypothesis;  let  us 
consider  in  what  way  this  hypothesis  is  expressible  in  terms 
of  the  general  doctrine  of  evolution.  Already  it  has  been 
pointed  out  that  the  evolving  of  modified  types  by  "  natural 
selection  or  the  preservation  of  favoured  races  in  the  struggle 
for  life,"  must  be  a  process  of  equilibration;  since  it  results 
in  the  production  of  organisms  which  are  in  equilibrium  with 
their  environments.  At  the  outset  of  this  chapter,  something 
was  done  towards  showing  how  this  continual  survival  of  the 
fittest  may  be  understood  as  the  progressive  establishment 
of  a  balance  between  inner  and  outer  forces.  Here,  however, 
we  must  consider  the  matter  more  closely. 

On  previous  occasions  we  have  contemplated  the  assem- 
blage of  individuals  composing  a  species,  as  an  aggregate 
in  a  state  of  moving  equilibrium.  We  have  seen  that  its 
powers  of  multiplication  give  it  an  expansive  energy  which  is 
antagonized  by  other  energies;  and  that  through  the  rhyth- 
mical variations  in  these  two  sets  of  energies  there  is  main- 
tained an  oscillating  limit  to  its  habitat,  and  an  oscillating 
limit  to  its  numbers.  On  another  occasion  (§96)  it  was 
shown  that  the  aggregate  of  individuals  constituting  a 
species,  has  a  kind  of  general  life  which,  "  like  the  life  of  an 
individual,  is  maintained  by  the  unequal  and  ever-varying 
actions  of  incident  forces  on  its  different  parts."  We  saw 
that  "  just  as,  in  each  organism,  incident  forces  constantly 
produce  divergences  from  the  mean  state  in  various  direc- 
tions, which  are  constantly  balanced  by  opposite  divergences 
indirectly  produced  by  other  incident  forces ;  and  just  as  the 
combination  of  rhythmical  functions  thus  maintained,  con- 
stitutes the  life  of  the  organism;  so,  in  a  species  there  is, 
through  gamogenesis,  a  perpetual  neutralization  of  those  con- 
trary deviations  from  the  mean  state,  which  are  ca'used  in  its 
different  parts  by  different  sets  of  incident  forces;  and  it  is 
similarly  by  the  rhythmical  production  and  compensation  of 


544  THE  EVOLUTION  OP  LIFE. 

these  contrary  deviations  that  the  species  continues  to  live." 
Hence,  to  understand  how  a  species  is  affected  by  causes 
which  destroy  some  of  its  units  and  favour  the  multiplication 
of  others,  we  must  consider  it  as  a  whole  whose  parts  are 
held  together  by  complex  forces  that  are  ever  re-balancing 
themselves — a  whole  whose  moving  equilibrium  is  continu- 
ally disturbed  and  continually  rectified.  Thus  much 
premised,  let  us  next  call  to  mind  how  moving  equilibria  in 
general  are  changed.  In  the  first  place,  a  new  incident  force 
falling  on  any  part  of  an  aggregate  with  balanced  motions, 
produces  a  new  motion  in  the  direction  of  least  resistance. 
In  the  second  place,  the  new  incident  force  is  gradually  used 
up  in  overcoming  the  opposing  forces,  and  when  it  is  a1! 
expended  the  opposing  forces  produce  a  recoil — a  rever.;e 
deviation  which  counter-balances  the  original  deviation. 
Consequently,  to  consider  whether  the  moving  equilibrium  of 
a  species  is  modified  in  the  same  way  as  moving  equilibria  in 
general,  is  to  consider  whether,  when  exposed  to  a  new  force, 
a  species  yields  in  the  direction  of  least  resistance;  and 
whether,  by  its  thus  yielding,  there  is  generated  in  the  species 
a  compensating  change  in  the  opposite  direction.  We  shall 
find  that  it  does  both  these  things. 

For  what,  expressed  in  mechanical  terms,  is  the  effect 
wrought  on  a  species  by  some  previously-unknown  enemy, 
that  kills  such  of  its  members  as  fail  in  defending  them- 
selves? The  disappearance  of  those  individuals  which  meet 
the  destroying  forces  by  the  smallest  preserving  forces,  is 
tantamount  to  the  yielding  of  the  species  as  a  whole  at  the 
places  where  the  resistances  are  the  least.  Or  if  by  some 
general  influence,  such  as  alteration  of  climate,  the  members 
of  a  species  are  subject  to  increase  of  external  actions 
which  are  ever  tending  to  overthrow  their  equilibria,  and 
which  they  are  ever  counter-balancing  by  certain  physiolo- 
gical actions,  which  are  the  first  to  die?  Those  least  able 
to  generate  the  internal  energies  which  antagonize  these 
external  energies.  If  the  change  be  an  increase  of  the 


INDIRECT  EQUILIBRATION.  545 

winter's  cold,  then  such  members  of  the  species  as  have 
unusual  powers  of  getting  food  or  of  digesting  food;  or  such 
as  are  by  their  constitutional  aptitude  for  making  fat,  fur- 
nished with  reserve  stores  of  force,  available  in  times  of 
scarcity,  or  such  as  have  the  thickest  coats  and  so  lose  least 
heat  by  radiation,  survive;  and  their  survival  implies  that 
in  each  of  them  the  moving  equilibrium  of  functions  presents 
such  an  adjustment  of  internal  forces,  as  prevents  over- 
throw by  the  modified  aggregate  of  external  forces.  Con- 
versely, the  members  which  die  are,  other  things  equal,  those 
deficient  in  the  power  of  meeting  the  new  action  by  an  equi- 
valent counter-action.  Thus,  in  all  cases,  a  species  con- 
sidered as  an  aggregate  in  a  state  of  moving  equilibrium, 
has  its  state  changed  by  the  yielding  of  its  fluctuating 
mass  wherever  this  mass  is  weakest  in  relation  to  the 
special  forces  acting  on  it.  The  conclusion  is,  indeed,  a 
truism.  But  now  what  must  follow  from  the  de- 

struction of  the  least-resisting  individuals  and  survival  of 
the  most-resisting  individuals  ?  On  the  moving  equilibrium 
of  the  species  as  a  whole,  existing  from  generation  to  gener- 
ation, the  effect  of  this  deviation  from  the  mean  state  is  to 
produce  a  compensating  deviation.  For  if  all  such  as  are 
deficient  of  power  in  a  certain  direction  are  destroyed,  what 
must  be  the  effect  on  posterity?  Had  they  lived  and  left 
offspring,  the  next  generation  would  have  had  the  same 
average  powers  as  preceding  generations:  there  would  have 
been  a  like  proportion  of  individuals  less  endowed  with  the 
needful  power,  and  individuals  more  endowed  with  it.  But 
the  more-endowed  individuals  being  alone  left  to  continue 
the  race,  there  must  result  a  new  generation  characterized 
by  a  larger  average  endowment  of  this  power.  That  is  to 
say,  on  the  moving  equilibrium  of  a  species,  an  action  pro- 
ducing change  in  a  given  direction  is  followed,  in  the  next 
generation,  by  a  reaction  producing  an  opposite  change. 
Observe,  too,  that  these  effects  correspond  in  their  degrees  of 
violence.  If  the  alteration  of  some  external  factor  is  so 


546  THE  EVOLUTION  OP  LIFE. 

great  that  it  leaves  alive  only  the  few  individuals  possessing 
extreme  endowments  of  the  power  required  to  antagonize  it; 
then,  in  succeeding  generations,  there  is  a  rapid  multiplica- 
tion of  individuals  similarly  possessing  extreme  endowments 
of  this  power — the  force  impressed  calls  out  an  equivalent 
conflicting  force.  Moreover,  the  change  is  temporary  where 
the  cause  is  temporary,  and  permanent  where  the  cause  is 
permanent.  All  that  are  deficient  in  the  needful  attribute 
having  been  killed  off,  and  the  survivors  having  the  needful 
attribute  in  a  comparatively  high  degree,  there  will  descend 
from  them,  not  only  some  possessing  equal  amounts  of  this 
attribute  with  themselves,  but  also  some  possessing  less 
amounts  of  it.  If  the  destructive  agency  has  not  continued 
in  action,  such  less-endowed  individuals  will  multiply;  and 
the  species,  after  sundry  oscillations,  will  return  to  its  pre- 
vious mean  state.  But  if  this  agency  be  a  persistent  one, 
such  less  endowed  individuals  will  be  continually  killed  off, 
and  eventually  none  but  highly-endowed  individuals  will  be 
produced — a  new  moving  equilibrium,  adapted  to  the  new 
environing  conditions,  will  result. 

It  may  be  objected  that  this  mode  of  expressing  the  facts 
does  not  include  the  cases  in  which  a  species  becomes  modified 
in  relation  to  surrounding  agencies  of  a  passive  kind — cases 
like  that  of  a  plant  which  acquires  hooked  seed-vessels,  by 
which  it  lays  hold  of  the  skins  of  passing  animals,  and  makes 
them  the  distributors  of  its  seeds — cases  in  which  the  outer 
agency  has  no  direct  tendency  at  first  to  affect  the  species, 
but  in  which  the  species  so  alters  itself  as  to  take  advantage 
of  the  outer  agency.  To  cases  of  this  kind,  however,  the 
same  mode  of  interpretation  applies  on  simply  changing  the 
terms.  While,  in  the  aggregate  of  influences  amid  which  a 
species  exists,  there  are  some  which  tend  to  overthrow  the 
moving  equilibria  of  its  members,  there  are  others  which 
facilitate  the  maintenance  of  their  moving  equilibria,  and 
some  which  are  capable  of  giving  their  moving  equilibria 
increased  stability:  instance  the  spread  into  their  habitat  of 


INDIRECT  EQUILIBRATION.  547 

some  now  kind  of  prey,  which  is  abundant  at  seasons  when 
other  prey  is  scarce.  Now  what  is  the  process  by  which  the 
moving  equilibrium  in  any  species  becomes  adapted  to  some 
additional  external  factor  furthering  its  maintenance?  In- 
stead of  an  increased  resistance  to  be  met  and  counter- 
balanced, there  is  here  a  diminished  resistance;  and  the 
diminished  resistance  is  equilibrated  in  the  same  way  as  the 
increased  resistance.  As,  in  the  one  case,  there  is  a  more 
frequent  survival  of  individuals  whose  peculiarities  enable 
them  to  resist  the  new  adverse  factor;  so,  in  the  other  case, 
there  is  a  more  frequent  survival  of  individuals  whose  pecu- 
liarities enable  them  to  take  advantage  of  the  new  favourable 
factor.  In  each  memb?r  of  the  species,  the  balance  of  func- 
tions and  correlated  arrangement  of  structures,  differ  slightly 
from  those  existing  in  other  members.  To  say  that  among 
all  its  members,  one  is  better  fitted  than  the  rest  to  benefit 
by  some  before-unused  agency  in  the  environment,  is  to  say 
that  its  moving  equilibrium  is,  in  so  far,  more  stably  adjusted 
to  the  sum  of  surrounding  influences.  And  if,  consequently, 
this  individual  maintains  its  moving  equilibrium  when  others 
fail,  and  has  offspring  which  $0  the  like — that  is,  if  indivi- 
duals thus  characterized  multiply  and  supplant  the  rest; 
there  is,  as  before,  a  process  which  effects  equilibration  be- 
tween the  organism  and  its  environment,  not  immediately 
but  mediately,  through  the  continuous  intercourse  between 
the  species  as  a  whole  and  the  environment. 

§  168.  Thus  we  see  that  indirect  equilibration  does  what- 
ever direct  equilibration  cannot  do.  All  these  processes  by 
which  organisms  are  re-fitted  to  their  ever-changing  environ- 
ments, must  be  equilibrations  of  one  kind  or  other.  As 
authority  for  this  conclusion,  we  have  not  simply  the  uni- 
versal truth  that  change  of  every  order  is  towards  equili- 
brium; but  we  have  also  the  truth  that  life  itself  is  a 
moving  equilibrium  between  inner  and  outer  actions — a  con- 
tinuous adjustment  of  internal  relations  to  external  relations ; 


548  THE  EVOLUTION  OF  LIFE. 

or  the  maintenance  of  a  balance  between  the  forces  to  which 
an  organism  is  subject  and  the  forces  which  it  evolves.  Hence 
all  changes  which  enable  a  species  to  live  under  altered  con- 
ditions, are  changes  towards  equilibrium  with  the  altered 
conditions;  and  therefore  those  which  do  not  come  within 
the  class  of  direct  equilibrations,  must  come  within  the  class 
of  indirect  equilibrations. 

And  now  we  reach  an  interpretation  of  Natural  Selection 
regarded  as  a  part  of  Evolution  at  large.  As  understood  in 
First  Principles,  Evolution  is  a  continuous  redistribution  of 
matter  and  motion;  and  a  process  of  evolution  which  is  not 
expressible  in  terms  of  matter  and  motion  has  not  been 
reduced  to  its  ultimate  form.  The  conception  of  Natural 
Selection  is  manifestly  one  not  known  to  physical  science: 
its  terms  are  not  of  a  kind  physical  science  can  take  cognis- 
ance of.  But  here  we  have  found  in  what  manner  it  may 
be  brought  within  the  realm  of  physical  science.  Kejecting 
metaphor  we  see  that  the  process  called  Natural  Selection  is 
literally  a  survival  of  the  fittest;  and  the  outcome  of  the 
above  argument  is  that  survival  of  the  fittest  is  a  maintenance 
of  the  moving  equilibrium  of  the  functions  in  presence  of 
outer  actions :  implying  the  possession  of  an  equilibrium 
which  is  relatively  stable  in  contrast  with  the  unstable 
equilibria  of  those  which  do  not  survive. 


CHAPTER   XIII. 

THE    CO-OPERATION    OF    THE    FACTORS. 

§  1G9.  THUS  the  phenomena  of  Organic  Evolution  may  be 
interpreted  in  the  same  way  as  the  phenomena  of  all  other 
Evolution.  Fully  to  see  this,  it  will  be  needful  for  us  to  con- 
template in  their  ensemble,  the  several  processes  separately 
described  in  the  four  preceding  chapters. 

If  the  forces  acting  on  any  aggregate  remain  the  same,  the 
changes  produced  by  them  will  presently  reach  a  limit,  at 
which  the  outer  forces  are  balanced  by  the  inner  forces;  and 
thereafter  no  further  metamorphosis  will  take  place.  Hence, 
that  there  may  be  continuous  changes  of  structure  in  organ- 
isms, there  must  be  continuous  changes  in  the  incident 
forces.  This  condition  to  the  evolution  of  animal  and  vegetal 
forms,  we  find  to  be  fully  satisfied.  The  astronomic,  geologic, 
and  meteorologic  changes  that  have  been  slowly  but  inces- 
santly going  on,  and  have  been  increasing  in  the  complexity 
of  their  combinations,  have  been  perpetually  altering  the 
circumstances  of  organisms;  and  organisms,  becoming  more 
numerous  in  theii  kinds  and  higher  in  their  kinds,  have  been 
perpetually  altering  one  another's  circumstances.  Thus,  for 
those  progressive  modifications  upon  modifications  which  or- 
ganic evolution  implies,  we  find  a  sufficient  cause.  The 
increasing  inner  changes  for  which  we  thus  find  a  cause  in 
the  perpetual  outer  changes,  conform,  so  far  as  we  can  trace 
them,  to  the  universal  law  of  the  instability  of  the  homo- 

36  549 


550  THE  EVOLUTION  OF  LIFE. 

geneous.  In  organisms,  as  in  all  other  things,  the  exposure 
of  different  parts  to  different  kinds  and  amounts  of  incident 
forces,  has  necessitated  their  differentiation;  and,  for  the 
like  reason,  aggregates  of  individuals  have  been  lapsing  into 
varieties,  and  species,  and  genera,  and  orders.  Further,  in 
each  type  of  organism,  as  in  the  aggregate  of  types,  the  mul- 
tiplication of  effects  has  continually  aided  this  transition  from 
a  more  homogeneous  to  a  more  heterogeneous  state.  And 
yet  again,  that  increasing  segregation  and  concomitant  in- 
creasing definiteness,  associated  with  the  growing  hetero- 
geneity of  organisms,  has  been  aided  by  the  continual  de- 
struction of  those  which  expose  themselves  to  aggregates  of 
external  actions  markedly  incongruous  with  the  aggregates 
of  their  internal  actions,  and  the  survival  of  those  subject 
only  to  comparatively  small  incongruities.  Finally, 

we  have  found  that  each  change  of  structure,  superposed  on 
preceding  changes,  has  been  a  re-equilibration  necessitated 
by  the  disturbance  of  a  preceding  equilibrium.  The  mainte- 
nance of  life  being  the  maintenance  of  a  balanced  combina- 
tion of  functions,  it  follows  that  individuals  and  species  that 
have  continued  to  live,  are  individuals  and  species  in  which 
the  balance  of  functions  has  not  been  overthrown.  Hence 
survival  through  successive  changes  of  conditions,  implies 
successive  adjustments  of  the  balance  to  the  new  conditions. 

The  actions  that  are  here  specified  in  succession,  are  in 
reality  simultaneous;  and  they  must  be  so  conceived  before 
organic  evolution  can  be  rightly  understood.  Some  aid 
towards  so  conceiving  them  will  be  given  by  the  annexed 
table,  representing  the  co-operation  of  the  factors. 

§  170.  Eespecting  this  co-operation,  it  remains  only  to 
point  out  the  respective  shares  of  the  factors  in  producing 
the  total  result;  and  the  way  in  which  the  proportions  of 
their  respective  shares  vary  as  evolution  progresses. 

At  first,  changes  in  the  amounts  and  combinations  of  inor- 
ganic forces,  astronomic,  geologic,  and  meteorologic,  were  the 


THE  CO-OPERATION  OF  THE  FACTORS. 


551 


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552  THE  EVOLUTION  OP  LIFE. 

only  causes  of  the  successive  modifications;  and  these 
changes  have  continued  to  be  causes.  But  as,  through  the 
diffusion  of  organisms  and  consequent  differential  actions  of 
inorganic  forces,  there  arose  unlikenesses  among  them,  pro- 
ducing varieties,  species,  genera,  orders,  classes,  the  actions 
of  organisms  on  one  another  became  new  sources  of  organic 
modifications.  And  as  fast  as  types  have  multiplied  and 
become  more  complex,  so  fast  have  the  mutual  actions  of 
organisms  come  to  be  more  influential  factors  in  their  re- 
spective evolutions :  eventually  becoming  the  chief  factors. 

Passing  from  the  external  causes  of  change  to  the  internal 
processes  of  change  entailed  by  them,  we  see  that  these,  too, 
have  varied  in  their  proportions:  that  which  was  originally 
the  most  important  and  almost  the  sole  process,  becoming 
gradually  less  important,  if  not  at  last  the  least  important. 
Always  there  must  have  been,  and  always  there  must  con- 
tinue to  be,  a  survival  of  the  fittest;  natural  selection  must 
have  been  in  operation  at  the  outset,  and  can  never  cease  to 
operate.  While  yet  organisms  had  small  abilities  to  co- 
ordinate their  actions,  and  adjust  them  to  environing  actions, 
natural  selection  worked  almost  alone  in  moulding  and  re- 
moulding organisms  into  fitness  for  their  changing  environ- 
ments; and  natural  selection  has  remained  almost  the  sole 
agency  by  which  plants  and  inferior  orders  of  animals 
have  been  modified  and  developed.  The  equilibration  of 
organisms  that  are  almost  passive,  is  necessarily  effected  in- 
directly, by  the  action  of  incident  forces  on  the  species  as  a 
whole.  But  along  with  the  evolution  of  organisms  having 
some  activity,  there  grows  up  a  kind  of  equilibration  which 
is  in  part  direct.  In  proportion  as  the  activity  increases 
direct  equilibration  plays  a  more  important  part.  Until, 
when  the  nervo-muscular  apparatus  becomes  greatly  deve- 
loped, and  the  power  of  varying  the  actions  to  fit  the  varying 
requirements  becomes  considerable,  the  share  taken  by  direct 
equilibration  rises  into  co-ordinate  importance  or  greater 
importance.  As  fast  as  essential  faculties  multiply,  and  as 


THE  CO-OPERATION  OP  THE  FACTORS.  553 

fast  as  the  number  of  organs  which  co-operate  in  any  given 
function  increases,  indirect  equilibration  through  natural 
selection  becomes  Jess  and  less  capable  of  producing  specific 
adaptations;  and  remains  capable  only  of  maintaining  the 
general  fitness  of  constitution  to  conditions.  The  production 
of  adaptations  by  direct  equilibration  then  takes  the  first 
place:  indirect  equilibration  serving  to  facilitate  it.  Until 
at  length,  among  the  civilized  human  races,  the  equilibration 
becomes  mainly  direct:  the  action  of  natural  selection  being 
limited  to  the  destruction  of  those  who  are  constitutionally 
too  feeble  to  live,  even  with  external  aid.  As  the  preserva- 
tion of  incapables  is  secured  by  our  social  arrangements; 
and  as  very  few  save  incarcerated  criminals  are  prevented  by 
their  inferiorities  from  leaving  the  average  number  of  off- 
spring; it  results  that  survival  of  the  fittest  can  scarcely  at 
all  act  in  such  way  as  to  produce  specialities  of  nature,  either 
bodily  or  mental.  Here  the  specialities  of  nature,  chiefly 
mental,  which  we  see  produced,  and  which  are  so  rapidly 
produced  that  a  few  centuries  show  a  considerable  change, 
must  be  ascribed  almost  wholly  to  direct  equilibration.* 

*  As  bearing  on  the  question  of  the  varieties  of  Man,  let  me  here  refer 
to  a  paper  on  "  The  Origin  of  the  Human  Races "  read  before  the  Anthro- 
pological Society,  March  1st,  1864,  by  Mr.  Alfred  Wallace.  In  this  paper, 
Mr.  Wallace  shows  that  along  with  the  attainment  of  that  intejligence 
implied  by  the  use  of  implements,  clothing,  &c.,  there  arises  a  tendency  for 
modifications  of  brain  to  take  the  place  of  modifications  of  body :  still,  how- 
ever, regarding  the  natural  selection  of  spontaneous  variations  as  the  cause 
of  the  modifications.  But  if  the  foregoing  arguments  be  valid,  natural 
selection  here  plays  but  the  secondary  part  of  furthering  the  adaptations 
otherwise  caused.  "  It  is  true  that,  as  Mr.  Wallace  argues,  and  as  I  have 
myself  briefly  indicated  (see  Westminster  Review,  for  April,  1862,  pp.  496— 
601),  the  natural  selection  of  races  leads  to  the  survival  of  the  more 
cerebrally-dcveloped,  while  the  less  ccrebrally-developed  disappear.  But 
though  natural  selection  acts  freely  in  the  struggle  of  one  society  with 
another;  yet,  among  the  units  of  each  society,  its  action  is  so  interfered 
with  that  there  remains  no  adequate  cause  for  the  acquirement  of  mental 
superiority  by  one  race  over  another,  except  the  inheritance  of  functionally- 
produced  modifications. 


CHAPTER   XIV. 

THE    CONVERGENCE    OF  THE    EVIDENCES. 

§  171.  OF  the  three  classes  of  evidences  that  have  been 
assigned  in  proof  of  Evolution,  the  a  priori,  which  we  took 
first,  were  partly  negative,  partly  positive. 

On  considering  the  "  General  Aspects  of  the  Special-crea- 
tion hypothesis,"  we  discovered  it  to  be  worthless.  Dis- 
credited by  its  origin,  and  wholly  without  any  basis  of 
observed  fact,  we  found  that  it  was  not  even  a  thinkable 
hypothesis;  and,  while  thus  intellectually  illusive,  it  turned 
out  to  have  moral  implications  irreconcilable  with  the  pro- 
fessed beliefs  of  those  who  hold  it. 

Contrariwise,  the  "  General  Aspects  of  the  Evolution- 
hypothesis "  begot  the  stronger  faith  in  it  the  more  nearly 
they  were  considered.  By  its  lineage  and  its  kindred,  it  was 
found  to  be  as  closely  allied  with  the  proved  truths  of  modern 
science,  as  is  the.  antagonist  hypothesis  with  the  proved 
errors  of  ancient  ignorance.  We  saw  that  instead  of  being 
a  mere  pseud-idea,  it  admits  of  elaboration  into  a  definite 
conception:  so  showing  its  legitimacy  as  an  hypothesis.  In- 
stead of  positing  a  purely  fictitious  process,  the  process  which 
it  alleges  proves  to  be  one  actually  going  on  around  us.  To 
which  add  that,  morally  considered,  this  hypothesis  presents 
no  radical  incongruities. 

Thus,  even  were  we  without  further  means  of  judging, 
554 


THE  CONVERGENCE  OP  THE  EVIDENCES.          555 

there  could  be  no  rational  hesitation  which  of  the  two  views 
should  be  entertained. 

§  172.  Further  means  of  judging,  however,  we  found  to 
be  afforded  by  bringing  the  two  hypotheses  face  to  face  with 
the  general  truths  established  by  naturalists.  These  induc- 
tive evidences  were  dealt  with  in  four  chapters. 

"The  Arguments  from  Classification"  were  these.  Organ- 
isms fall  into  groups  within  groups ;  and  this  is  the  arrange- 
ment which  we  see  results  from  evolution,  where  it  is  known 
to  take  place.  Of  these  groups  within  groups,  the  great  or 
primary  ones  are  the  most  unlike,  the  sub-groups  are  less 
unlike,  the  sub-sub-groups  still  less  unlike,  and  so  on;  and 
this,  too;  is  a  characteristic  of  groups  demonstrably  produced 
by  evolution.  Moreover,  indefiniteness  of  equivalence  among 
the  groups  is  common  to  those  which  we  know  have  been 
evolved,  and  those  here  supposed  to  have  been  evolved.  And 
then  there  is  the  further  significant  fact,  that  divergent 
groups  are  allied  through  their  lowest  rather  than  their  high- 
est members. 

Of  "  the  Arguments  from  Embryology,"  the  first  is  that 
when  developing  embryos  are  traced  from  their  common 
starting  point,  and  their  divergences  and  re-divergences 
symbolized  by  a  genealogical  tree,  there  is  manifest  a  general 
parallelism  between  the  arrangement  of  its  primary,  second- 
ary, and  tertiary  branches,  and  the  arrangement  of  the  di- 
visions and  sub-divisions  of  our  classifications.  Nor  do  the 
minor  deviations  from  this  general  parallelism,  which  look 
like  difficulties,  fail,  on  closer  observation,  to  furnish  addi- 
tional evidence;  since  those  traits  of  a  common  ancestry 
which  embryology  reveals,  are,  if  modifications  have  resulted 
from  changed  conditions,  liable  to  be  disguised  in  different 
ways  and  degrees  in  different  lines  of  descendants. 

We  next  considered  "  the  Arguments  from  Morphology." 
Apart  from  those  kinships  among  organisms  disclosed  by 
their  developmental  changes,  the  kinships  which  their  adult 


556  THE  EVOLUTION  OF  LIFE. 

forms  show  are  profoundly  significant.  The  unities  of  type 
found  under  such  different  externals,  are  inexplicable  except 
as  results  of  community  of  descent  with  non-community  of 
modification.  Again,  each  organism  analyzed  apart,  shows, 
in  the  likenesses  obscured  by  unlikenesses  of  its  component 
parts,  a  peculiarity  which  can  be  ascribed  only  to  the  formation 
of  a  more  heterogeneous  organism  out  of  a  more  homogeneous 
one.  And  once  more,  the  existence  of  rudimentary  organs, 
homologous  with  organs  that  are  developed  in  allied  animals 
or  plants,  while  it  admits  of  no  other  rational  interpretation, 
is  satisfactorily  interpreted  by  the  hypothesis  of  evolution. 

Last  of  the  inductive  evidences,  came  "  the  Arguments 
from  Distribution."  While  the  facts  of  distribution  in  Space 
are  unaccountable  as  results  'of  designed  adaptation  of  organ- 
isms to  their  habitats,  they  are  accountable  as  results  of  the 
competition  of  species,  and  the  spread  of  the  more  fit  into 
the  habitats  of  the  lesi  fit,  followed  by  the  changes  which 
new  conditions  induce.  Though  the  facts  of  distribution  in 
Time  are  so  fragmentary  that  no  positive  conclusion  can  be 
drawn,  yet  all  of  them  are  reconcilable  with  the  hypothesis 
of  evolution,  and  some  of  them  yield  it  strong  support : 
especially  the  near  relationship  existing  between  the  living 
and  extinct  types  in  each  great  geographical  area. 

Thus  of  these  four  groups,  each  furnished  several  argu- 
ments which  point  to  the  same  conclusion;  and  the  conclu- 
sion pointed  to  by  the  arguments  of  any  one  group,  is  that 
pointed  to  by  the  arguments  of  every  other  group.  This 
coincidence  of  coincidences  would  give  to  the  induction  a 
very  high  degree  of  probability,  even  were  it  not  enforced  by 
deduction.  But  the  conclusion  deductively  reached,  is  in 
harmony  with  the  inductive  conclusion. 

§  173.  Passing  from  the  evidence  that  evolution  has  taken 
place,  to  the  question — How  has  it  taken  place?  we  find  in 
known  agencies  and  known  processes,  adequate  causes  of  its 
phenomena. 


THE  CONVERGENCE  OF  THE  EVIDENCES.  557 

In  astronomic,  geologic,  and  meteorologic  changes,  ever  in 
progress,  ever  combining  in  new  and  more  involved  ways, 
we  have  a  set  of  inorganic  factors  to  which  all  organisms  are 
exposed;  and  in  the  varying  and  complicating  actions  of 
organisms  on  one  another,  we  have  a  set  of  organic  factors 
that  alter  with  increasing  rapidity.  Thus,  speaking  generally, 
all  members  of  the  Earth's  Flora  and  Fauna  experience  per- 
petual re-arrangements  of  external  forces. 

Each  organic  aggregate,  whether  considered  individually 
or  as  a  continuously-existing  species,  is  modified  afresh  by 
each  fresh  distribution  of  external  forces.  To  its  pre-existing 
differentiations  new  differentiations  are  added ;  and  thus  that 
lapse  to  a  more  heterogeneous  state,  which  would  have  a  fixed 
limit  were  the  circumstances  fixed,  has  its  limit  perpetually 
removed  by  the  perpetual  change  of  the  circumstances. 

These  modifications  upon  modifications  which  result  in 
evolution  structurally  considered,  are  the  accompaniments 
of  those  functional  alterations  continually  required  to  re- 
equilibrate  inner  with  outer  actions.  That  moving  equi- 
librium of  inner  actions  corresponding  with  outer  actions, 
which  constitutes  the  life  of  an  organism,  must  either  be 
overthrown  by  a  change  in  the  outer  actions,  or  must  undergo 
perturbations  that  cannot  end  until  there  is  a  re-adjusted 
balance  of  functions  and  correlative  adaptation  of  structures. 

But  where  the  external  changes  are  cither  such  as  are 
fatal  when  experienced  by  the  individuals,  or  such  as  act  on 
,the  individuals  in  ways  that  do  not  affect  the  equilibrium  of 
their  functions;  then  the  re-adjustment  results  through  the 
effects  produced  on  the  species  as  a  whole — there  is  indirect 
equilibration.  By  the  preservation  in  successive  generations 
of  those  whose  moving  equilibria  are  least  at  variance  with 
the  requirements,  there  is  produced  a  changed  equilibrium 
completely  in  harmony  with  the  requirements. 

§  174.  Even  were  this  the  whole  of  the  evidence  assign- 
able for  the  belief  that  organisms  have  been  gradually  evolved, 


558  THE  EVOLUTION  OF  LIFE. 

it  would  have  a  warrant  higher  than  that  of  many  beliefs 
which  are  regarded  as  established.  But  the  evidence  is  far 
from  exhausted. 

At  the  outset  it  was  remarked  that  the  phenomena  pre- 
sented by  the  organic  world  as  a  whole,  cannot  be  properly 
dealt  with  apart  from  the  phenomena  presented  by  each 
organism,  in  the  course  of  its  growth,  development,  and 
decay.  The  interpretation  of  either  implies  interpretation  of 
the  other;  since  the  two  are  in  reality  parts  of  one  process. 
Hence,  the  validity  of  any  hypothesis  respecting  the  one 
class  of  phenomena,  may  be  tested  by  its  congruity  with 
phenomena  of  the  other  class.  We  are  now  about  to  pass 
to  the  more  special  phenomena  of  development,  as  displayed 
in  the  structures  and  functions  of  individual  organisms.  If 
the  hypothesis  that  plants  and  animals  have  been  progres- 
sively .evolved  be  true,  it  must  furnish  us  with  keys  to  these 
phenomena.  We  shall  find  that  it  does  this;  and  by  doing 
it  gives  numberless  additional  vouchers  for  its  truth. 


CHAPTER  XIVA. 

RECENT    CRITICISMS    AND    HYPOTHESES. 

§  174a.  SINCE  the  first  edition  of  this  work  was  published, 
and  more  especially  since  the  death  of  Mr.  Darwin,  an  active 
discussion  of  the  Evolution  hypothesis  has  led  to  some  sig- 
nificant results. 

That  organic  evolution  has  been  going  on  from  the  dawn 
of  life  down  to  the  present  time,  is  now  a  belief  almost 
universally  accepted  by  zoologists  and  botanists — "  almost 
universally,"  I  say,  because  the  surviving  influence  of  Cuvier 
prevents  acceptance  of  it  by  some  of  them  in  France.  Omit- 
ting the  ideas  of  these,  all  biological  interpretations,  specu- 
lations, and  investigations,  tacitly  assume  that  organisms 
of  every  kind  in  every  era  and  in  every  region  have  come 
into  existence  by  the  process  of  descent  with  modifica- 
tion. 

But  while  concerning  the  fact  of  evolution  there  is  agree- 
ment, concerning  its  causes  there  is  disagreement.  The 
ideas  of  naturalists  have,  in  this  respect,  undergone  a  dif- 
ferentiation increasingly  pronounced ;  which  has  ended  in 
the  production  of  two  diametrically  opposed  beliefs.  The 
cause  which  Mr.  Darwin  first  made  conspicuous  has  come  to 
be  regarded  by  some  as  the  sole  cause;  while,  on  the  part  of 
others  there  has  been  a  growing  recognition  of  the  cause 
which  he  at  first  disregarded  but  afterwards  admitted. 
Prof.  Weismann  and  his  supporters  contend  that  natural 
selection  suffices  to  explain  everything.  Contrariwise,  among 

559 


560  TOE  EVOLUTION  OP  LIFE. 

many  who  recognize  the  inheritance  of  functionally-produced 
changes,  there  are  a  few,  like  the  Eev.  Prof.  Henslow,  who 
regard  it  as  the  sole  factor. 

The  foregoing  chapters  imply  that  the  beliefs  of  neither 
extreme  are  here  adopted.  Agreeing  with  Mr.  Darwin  that 
hoth  factors  have  been  operative,  I  hold  that  the  inheritance 
of  functionally-caused  alterations  has  played  a  larger  part 
than  he  admitted  even  at  the  close  of  his  life;  and  that, 
coming  more  to  -the  front  as  evolution  has  advanced,  it  has 
played  the  chief  part  in  producing  the  highest  types.  I  am 
not  now  about  to  discuss  afresh  these  questions,  but  to  deal 
with  certain  further  questions. 

For  while  there  has  been  taking  place  in  the  biological 
world  the  major  differentiation  above  indicated,  there  have 
been  taking  place  certain  minor  differentiations — there  have 
been  arising  special  views  respecting  the  process  of  organic 
evolution.  Concerning  each  of  these  it  is  needful  to  say 
something. 

§  1746.  Among  the  implied  controversies  the  most  con- 
spicuous one  has  concerned  the  alleged  process  called  by 
Prof.  Weismann  Panmixia — a  process  which  Dr.  Eomanes 
had  foreshadowed  under  the  name  of  "  the  Cessation  of 
Selection."  Dr.  Komanes  says : — "  At  that  time  it  appeared 
to  me,  as  it  now  appears  to  Weismann,  entirely  to  supersede 
the  necessity  of  supposing  that  the  effect  of  disuse  is  ever 
inherited  in  any  degree  at  all."  *  The  alleged  mode  of  action 
is  exemplified  by  Prof.  Weismann  as  follows : — 

"A  goose  or  a  duck  must  possess  strong  powers  of  flight  in  the 
natural  state,  but  such  powers  are  no  longer  necessary  for  obtaining 
food  when  it  is  brought  into  the  poultry-yard,  so  that  a  rigid  selection 
of  individuals  with  well-developed  wings,  at  once  ceases  among  its 
descendants.  Hence  in  the  course  of  generations,  a  deterioration  of 
the  organs  of  flight  must  necessarily  ensue,  and  the  other  members 
and  organs  of  the  bird  will  be  similarly  affected."  t 

*  Darwin  md  after  Darwin,  Part  II,  p.  39. 
f  Essays  upon  Heredity,  vol.  i,  p.  PO. 


RECENT  CRITICISMS  AND  HYPOTHESES.  561 

Here,  and  throughout  the  arguments  of  those  who  accept 
the  hypothesis  of  Panmixia,  there  is  an  unwarranted  assump- 
tion— nay,  an  assumption  at  variance  with  the  doctrine  in 
support  of  which  it  is  made.  It  is  contended  that  in  such 
cases  as  the  one  given  there  will,  apart  from  any  effects  of 
disuse,  be  decrease  in  the  disused  organs  because,  not  being 
kept  by  Natural  Selection  up  to  the. level  of  strength  pre- 
viously needed,  they  will  vary  in  the  direction  of  decrease; 
and  that  variations  in  the  direction  of  decrease,  occurring  in 
some  individuals,  will,  by  interbreeding,  produce  an  average 
decrease  throughout  the  species.  But  why  will  the  disused 
organs  vary  in  the  direction  of  decrease  more  than  in  the 
direction  of  increase?  The  hypothesis  of  Natural  Selection 
postulates  indeterminate  variations — deviations  no  more  in 
one  direction  than  in  the  opposite  direction :  implying  that 
increases  and  decreases  of  size  will  occur  to  equal  extents 
and  with  equal  frequencies.  With  any  other  assumption  the 
hypothesis  lapses;  for  if  the  variations  in  one  direction 
exceed  those  in  another  the  question  arises — What  makes 
them  do  this?  And  whatever  makes  them  do  this  becomes 
the  essential  cause  of  the  -  modification :  the  selection  of 
favourable  variations  is  tacitly  admitted  to  be  an  insufficient 
explanation.  But  if  the  hypothesis  of  Natural  Selection 
itself  implies  the  occurrence  of  equal  variations  on  all  sides 
of  the  mean,  how  can  Panmixia  produce  decrease?  Plus 
deviations  will  cancel  minus  deviations,  and  the  organ  will 
remain  where  it  was.* 

*  In  a  letter  published  by  Dr.  Romanes  in  Nature,  for  April  26,  1894,  he 
alleges  three  reasons  why  "as  soon  as  selection  is  withdrawn  from  an  organ 
the  minus  variations  of  that  organ  outnumber  the  plus  variations."  The  first 
is  that  "  the  survival-mean  must  descend  to  the  birth-mean."  The  interpre- 
tation of  this  is  that  if  the  members  of  a  species  are  on  the  average  born 
with  an  organ  of  the  required  size,  and  if  they  are  exposed  to  natural  selec- 
tion, then  those  in  which  the  organ  is  relatively  small  will  some  of  them  die, 
and  consequently  the  mean  size  of  the  organ  at  adult  ag«  will  be  greater 
than  at  birth.  Contrariwise,  if  the  organ  becomes  useless  and  natural  selec- 
tion does  not  operate  on  it,  this  difference  between  the  birth-mean  and  the 
survival-mean  disappears.  Now  here,  again,  the  plus  variations  and  their 


562  THE  EVOLUTION  OP  LIFE. 

"  But  you  have  forgotten  the  tendency  to  economy  of 
growth/'  will  be  the  reply — "  you  have  forgotten  that  in  Mr. 
Darwin's  words  *  natural  selection  is  continually  trying  to 
economize  in  every  part  of  the  organization ; '  and  that  this 
is  a  constant  cause  favouring  minus  variations."  I  have  not 
forgotten  it;  but  have  remembered  it  as  showing  how,  to 
support  the  hypothesis  of  Panmixia,  there  is  invoked  the  aid 
of  that  very  hypothesis  which  it  is  to  replace.  For  this 
principle  of  economy  is  but  another  aspect  of  the  principle  of 
functionally-produced  modifications.  Xearly  forty  years  ago 
I  contended  that  "  the  different  parts  of  ...  an  individual 
organism  compete  for  nutriment;  and  severally  obtain  more 
or  less  of  it  according  as  they  are  discharging  more  or  less 
duty : "  *  the  implication  being  that  as  all  other  organs  are 
demanding  blood,  decrease  of  duty  in  any  one,  entailing  de- 
creased supply  of  blood,  brings  about  decreased  size.  In  other 
words,  the  alleged  economy  is  nothing  else  than  the. abstrac- 
tion, by  active  parts,  of  nutriment  from  an  inactive  part ;  and 
is  merely  another  name  for  functionally-produced  decrease. 
So  that  if  the  variations  are  supposed  to  take  place  pre- 

effects  are  ignored.  Supposing  the  organ  to  be  useful,  it  is  tacitly  assumed 
that  while  minus  variations  are  injurious,  plus  variations  are  not  injurious. 
This  is  untrue.  Superfluous  size  of  an  organ  implies  several  evils : — Its 
original  cost  is  greater  than  reciuisite,  and  other  organs  suffer;  the  con- 
tinuous cost  of  its  nutrition  is  unduly  great,  involving  further  injury;  it 
adds  needlessly  to  the  weight  carried  and  so  again  is  detrimental;  and  there 
is  in  some  cases  yet  a  further  mischief — it  is  in  the  way.  Clearly,  then, 
those  in  which  plus  variations  of  the  organ  have  occurred  are  likely  to  be 
killed  off  as  well  as  those  in  which  minus  variations  hare  occurred;  and 
hence  there  is  no  proof  that  the  survival-mean  will  exceed  the  birth-mean. 
Moreover  the  assumption  has  a  fatal  implication.  To  say  that  the  survival- 
mean  of  an  organ  is  greater  than  the  birth-mean  is  to  say  that  the  organ  is 
greater  in  proportion  to  other  organs  than  it  was  at  birth.  What  happens  if 
instead  of  one  organ  we  consider  all  the  organs  ?  If  the  survival-mean  of  a 
particular  organ  is  greater  than  its  birth-mean,  the  survival  mean  of  each 
other  organ  must  also  be  greater.  Thus  the  proposition  is  that  every  organ 
has  become  larger  in  relation  to  every  other  organ ! — a  marvellous  proposi- 
tion. I  need  only  add  that  Dr.  Romanes"  inferences  with  respect  to  the  two 
other  causes — atavism  and  failing  heredity — are  similarly  vitiated  by  ignoring 
the  plu*  variations  and  their  effects. 

*  Westminster  Review,  January,  1860.     See  also  Essays,  <tc.,  vol.  i,  p.  290. 


RECENT  CRITICISMS  AND  HYPOTHESES.  563 

dominantly  in  the  direction  of  decrease,  it  can  only  be  by 
silently  assuming  the  cause  which  is  overtly  denied. 

But  now  we  come  to  the  strange  fact  that  the  particular 
case  in  which  panmixia  is  assigned  in  disproof  of  alleged 
inheritance  of  functionally-produced  modifications,  is  a  case 
in  which  it  would  be  inapplicable  even  were  its  assumption 
legitimate — the  case  of  disused  organs  in  domestic  animals. 
For  since  nutrition  is  here  abundant,  the  principle  of  economy 
under  the  form  alleged  does  not  come  into  play.  Contrari- 
wise, there  even  occurs  a  partial  re-development  of  rudi- 
mentary organs :  instances  named  by  Mr.  Darwin  being  the 
supplementary  mammae  in  cows,  fifth  toes  on  the  hind  feet 
of  dogs,  spurs  and  comb  in  hens,  and  canine  teeth  in  mares. 
Now  clearly,  if  organs  disused  for  innumerable  generations 
may  thus  vary  in  the  direction  of  increase,  it  must,  a  fortiori, 
be  so  with  recently  disused  organs,  and  there  disappears  all 
plea  (even  the  illegitimate  plea)  for  assuming  that  in  the 
wing  of  a  wild  duck  which  has  become  domesticated,  the  minus 
variations  will  exceed  the  plus  variations:  the  hypothesis  of 
panmixia  loses  its  postulate. 

If  it  be  said  that  Mr.  Darwin's  argument  is  based  on  the 
changed  ratio  between  the  weights  of  leg-bones  and  wing- 
bones,  and  that  this  changed  ratio  may  result  not  from  de- 
crease of  the  wing-bones  but  from  increase  of  the  leg-bones, 
then  there  comes  a  fatal  reply.  Such  increase  cannot  be 
ascribed  to  selection  of  varieties,  since  there  is  no  selec- 
tive breeding  to  obtain  larger  legs,  and  as  it  is  not  pretended 
that  panmixia  accounts  for  increase  the  case  is  lost:  there 
remains  no  cause  for  such  increase  save  increase  of  function. 

§  174c.  The  doctrine  of  determinate  evolution  or  definitely- 
directed  evolution,  which  appears  to  be  in  one  form  or  other 
entertained  by  sundry  naturalists,  has  been  set  forth  by  the 
late  Prof.  Eimer  under  the  title  "  Orthogenesis."  A  distinct 
statement  of  his  conception  is  not  easily  made  for  the  reason 
that,  as  I  think,  the  conception  itself  is  indistinct.  Here  are 
some  extracts  from  a  translation  of  his  paper  published  at 


56±  THE  EVOLUTION  OF  LIFE. 

Chicago.  Out  of  these  the  reader  may  form  a  notion  of  the 
theory : 

"Orthogenesis  shows  that  organisms  develop  in  definite  directions 
without  the  least  regard  for  utility  through  purely  physiological  causes 
as  the  result  of  organic  growth,  as  I  term  the  process. " 

' '  I  am  concerned  in  this  paper  with  definitely  directed  evolution 
as  the  cause  of  transmutation,  and  not  with  the  effects  of  the  use  and 
activity  of  organs  which  with  Lamarck  I  adopted  as  the  second  main 
explanatory  cause  thereof." 

"The  causes  of  definitely  directed  evolution  are  contained,  accord- 
ing to  my  view,  in  the  effects  produced  by  outward  circumstances  and 
influences  such  as  climate  and  nutrition  upon  the  constitution  of  a 
given  organism." 

"At  variance  with  all  the  facts  of  definitely  directed  evolution 
...  is  also  the  contention  of  my  opponent  [Weismann]  .  .  . 
that  the  variations  demonstrably  oscillate  to  and  fro  in  the  most  di- 
verse directions  about  a  given  zero-point.  There  is  no  oscillation  in 
the  direction  of  development,  but  simply  an  advance  forwards  in  a 
straight  line  with  occasional  lateral  divergences  whereby  the  forkings 
of  the  ancestral  tree  are  produced. "  * 

These  sentences  contain  one  of  those  explanations  which 
explain  nothing;  for  we  are  not  enabled  to  see  how  the 
"  outward  circumstances  and  influences  "  produce  the  effects 
ascribed  to  them.  We  are  not  shown  in  what  way  they 
cause  organic  evolution  in  general,  still  less  in  what  way 
they  cause  the  infinitely-varied  forms  in  which  organic  evo- 
lution results.  The  assertion  that  evolution  takes  definitely- 
directed  lines  is  accompanied  by  no  indication  of  the  reasons 
why  particular  lines  are  followed  rather  than  others.  In 
short,  we  are  simply  taken  a  step  back,  and  for  further  in- 
terpretation referred  to  a  cause  said  to  be  adequate,  but  the 
operations  of  which  we  are  to  imagine  as  best  we  may. 

This  is  a  re-introduction  of  supernaturalism  under  a  dis- 
guise. It  may  pair  off  with  the  conception  made  popular  by 
the  Vestiges  of  the  Natural  History  of  Creation,  in  which  it 
was  contended  that  there  exists  a  persistent  tendency  towards 
the  birth  of  a  higher  form  of  creature ;  or  it  may  be  bracketed 
*  "  On  Orthogenesis  and  the  Impotence  of  Natural  Selection  in  Species- 
Formation,"  pp.  2,  19,  22,  24. 


RECENT  CRITICISMS  AND  HYPOTHESES.  565 

with  the  idea  entertained  by  the  late  Prof.  Owen,  who  alleged 
an  "  ordained  becoming  "  of  living  things. 

§  174d.  An  objection  to  the  Darwinian  doctrine  which  has 
risen  into  prominence,  is  that  Natural  Selection  does  not 
explain  that  which  it  professes  to  explain.  In  the  words  of 
Mr.  J.  T.  Cunningham: — 

"Everybody  knows  that  the  theory  of  natural  selection  was  put  for- 
ward by  Darwin  as  a  theory  of  the  origin  of  species,  and  yet  it  is  only 
a  theory  of  the  origin  of  adaptations.  The  question  is :  Are  the  dif- 
ferences between  species  differences  of  adaptation  ?  If  so,  then  the 
origin  of  species  and  the  origin  of  adaptations  are  equivalent  terms. 
But  there  is  scarcely  a  single  instance  in  which  a  specific  character  has 
been  shown  to  be  useful,  to  be  adaptive."  * 

To  illustrate  this  last  statement  Mr.  Cunningham  names  the 
plaice,  flounder,  and  dab  as  three  flat  fishes  in  which,  along 
with  the  adaptive  characters  related  to  the  mode  of  life  com- 
mon to  them  all,  each  has  specific  characters  which  are  not 
adaptive.  Xo  evidence  is  forthcoming  that  these  in  any  way 
conduce  to  the  welfare  of  the  species.  Two  propositions  are 
here  involved  which  should  be  separately  dealt  with. 

The  first  is  that  the  adaptive  modifications  which  survival 
of  the  fittest  is  able  to  produce,  do  not  become  specific  traits : 
they  are  traits  separate  in  kind  from  those  which  mark  off 
groups  proved  to  be  specifically  distinct  by  their  inability  to 
breed  together.  Such  evidence  as  we  at  present  have  seems 
to  warrant  this  statement.  Out  of  the  many  varieties  of 
dogs  most,  if  not  all,  have  been  rendered  distinct  by  adaptive 
modifications,  mostly  produced  by  selection.  But,  notwith- 
standing the  immense  divergences  of  structure  so  produced, 
the  varieties  inter-breed.  To  this,  however,  it  may  be  replied 
that  sufficient  time  has  not  elapsed — that  the  process  by 
which  a  structural  adaptation  so  reacts  on  the  constitution 
as  to  make  it  a  distinct  one,  possibly,  or  probably,  takes 
many  thousands  of  years.  Let  us  accept  for  the  moment 
Lord  Kelvin's  low  estimate  of  the  geologic  time  during  which 

*  Address  to  Plymouth  Institution,  at  opening  of  Session  1895-6. 
37 


566  THE  EVOLUTION  OP  LIFE. 

life  has  existed — one  hundred  million  years.  Suppose  we 
divide  that  time  into  as  many  parts  as  there  are  hours  occu- 
pied in  the  development  of  a  human  foatus.  And  suppose 
that  during  these  hundred  million  years  there  has  been  going 
on  with  some  uniformity  the  evolution  of  the  various  organic 
types  now  existing.  Then  the  amount  of  change  undergone 
by  the  foetus  in  an  hour,  will  be  equivalent  to  the  amount 
of  change  undergone  by  an  evolving  organic  form  in  fifteen 
thousand  years.  That  is  to  say,  during  general  evolution  it 
may  have  taken  fifteen  thousand  years  to  establish,  as  dis- 
tinct, two  species  differing  from  one  another  no  more  than 
the  foetus  differs  from  itself  after  the  lapse  of  an  hour. 
Hence,  though  we  lack  proof  that  adaptive  modifications  be- 
come specific  traits,  it  is  quite  possible  that  they  are  in  course 
of  becoming  specific  traits. 

The  converse  proposition,  that  the  traits  by  which  species 
are  ordinarily  distinguished  are  non-adaptive  traits  is  well 
sustained;  and  the  statement  that,  if  not  themselves  useful 
they  are  correlated  with  those  which  are  useful,  is,  to  say  the 
least,  unproved.  For  the  instances  given  by  Mr.  Darwin  of 
correlated  traits  are  not  those  between  adaptive  traits  and 
the  traits  regarded  as  specific,  but  between  traits  none  of 
which  are  specific;  as  between  skull  and  limbs  in  swine, 
tusks  and  bristles  in  swine,  horns  and  wool  in  sheep,  beak 
and  feet  in  pigeons. 

If  we  seek  a  clue  in  those  processes  by  which  correlations 
are  brought  about — the  physiological  actions  and  reactions — 
we  may  at  once  see  that  any  organic  modification,  be  it 
adaptive  or  not,  must  entail  secondary  modifications  through- 
out the  rest  of  the  organism,  most  of  them  insensible  but 
some  of  them  sensible.  The  competition  for  blood  among 
organs,  referred  to  above,  necessitates  that,  other  things  re- 
maining the  same,  the  extra  growth  of  any  one  tells  on 
all  others,  in  variable  degrees  according  to  conditions,  and 
may  cause  appreciable  diminutions  of  some.  This  is  not 
all.  While  the  quantity  of  blood  supplied  to  other  organs  is 


RECENT  CRITICISMS  AND  HYPOTHESES.  567 

affected,  its  quality  also  is  in  some  cases  affected.  Each 
organ,  or  at  any  rate  each  class  of  organs,  has  special  nutri- 
tion— abstracts  from  the  blood  a  proportion  of  ingredients 
different  from  that  abstracted  by  other  organs  or  classes  of 
organs.  Hence  may  result  a  deficiency  or  a  surplus  of  some 
element:  instance  the  change  in  the  blood  which  must  be 
caused  by  growth  ef  a  stag's  antlers.  Now  if  such  effects  are 
always  produced,  and  if,  further,  a  change  of  general  nutri- 
tion caused  by  a  new  food  or  by  a  difference  of  ability  to 
utilize  certain  components  of  food,  similarly  operates  (in- 
stance the  above  named  correlation  between  horns  and  wool), 
then  every  modification  must  entail  throughout  the  organism 
multitudinous  alterations  of  structure.  Such  alterations 
will  ordinarily  be  neither  in  themselves  useful  nor  necessarily 
correlated  with  those  which  are  useful ;  since  they  must  arise 
as  concomitants  of  any  change,  whether  adaptive  or  not. 
There  will  consequently  arise  the  innumerable  minute  differ- 
ences presented  by  allied  species  in  addition  to  the  differences 
called  specific. 

On  joining  with  recognition  of  this  general  process  a  recog- 
nition of  the  tendency  towards  localization  of  deposit,  one 
possible  origin  of  specific  marks  is  suggested.  When  in  an 
organism  the  circulating  fluids  contain  useless  matter,  normal 
or  abnormal,  the  excretion  of  it,  once  determined  towards  a 
certain  place,  continues  at  that  place.  Trees  furnish  examples 
in  the  casting  out  of  gums  and  resins.  Animal  life  yields 
evidence  in  gouty  concretions  and  such  morbid  products  as 
tubercle.  A  place  of  enfeebled  nutrition  is  commonly 
chosen — not  unfrequently  a  place  where  a  local  injury  has 
occurred.  Now  if  we  extend  this  principle,  well  recognized 
in  pathological  processes,  to  physiological  processes,  we  may 
infer  that  where  an  adaptive  modification  has  so  reacted  on 
the  blood  as  to  leave  some  matter  to  be  got  rid  of,  the  deposit 
of  this,  initiated  at  some  place  of  least  resistance,  may  pro- 
duce a  local  structure  which  eventually  becomes  a  species- 
mark.  A  relevant  inquiry  suggests  itself — What  proportion 


568  THE  EVOLUTION  OF  LIFE. 

of  species-marks  are  formed  out  of  inanimate  tissue  or  tissue 
of  low  vitality — tissue  which,  like  hair,  feathers,  horns,  teeth, 
is  composed  of  by-products  unfit  for  carrying  on  vital 
actions. 

§  174e.  In  the  days  when,  not  having  been  better  in- 
structed by  Mr.  Darwin,  I  believed  that  all  changes  of  struc- 
ture in  organisms  result  from  changes  of  function,  I  held 
that  the  cause  of  such  changes  of  function  is  migration.  As- 
suming as  the  antecedent  of  migration  a  great  geologic 
change,  such  as  upheaval  of  the  East  Indian  Archipelago 
step  by  step  into  a  continent,  it  was  argued,  in  an  essay  I 
then  wrote,  that,  subjected  primarily  to  new  influences  in  its 
original  habitat,  each  kind  of  plant  and  animal  would  sec- 
ondarily be  subjected  to  the  altered  conditions  consequent 
on  spreading  over  the  upheaved  regions. 

"Each  species  being  distributed  over  an  area  of  some  extent,  and 
tending  continually  to  colonize  the  new  area  exposed,  its  different 
members  would  be  subject  to  different  sets  of  changes.  Plants  and 
animals  spreading  towards  the  equator  would  not  be  affected  in  the 
same  way  with  others  spreading  from  it.  Those  spreading  towards 
the  new  shores  would  undergo  changes  unlike  the  changes  undergone 
by  those  spreading  into  the  mountains.  Thus,  each  original  race  of 
organisms  would  become  the  root  from  which  diverged  several  races 
differing  more  or  less  from  it  and  from  one  another." 

It  was  further  argued  that,  beyond  modifications  caused  by 
change  of  physical  conditions  and  food,  others  would  be  caused 
by  contact  of  the  Flora  and  Fauna  of  each  island  with  the 
Floras  and  Faunas  of  other  islands:  bringing  experience  of 
animals  and  plants  before  unknown.* 

While  this  conception  was  wrong  in  so  far  as  it  ascribed 
the  production  of  new  species  entirely  to  inheritance  of 
functionally -wrought  alterations  (thus  failing  to  recognize 
Natural  Selection,  which  was  not  yet  enunciated),  it  was  right 
in  so  far  as  it  ascribed  organic  changes  to  changes  of  condi- 
tions. And  it  was,  I  think,  also  right  in  so  far  as  it  implied 
*  Westminster  Review,  April,  1857.  "Progress:  its  Law  and  Cause."  See 
also  Essays,  vol.  i. 


RECENT  CRITICISMS  AND  HYPOTHESES.  569 

that  isolation  is  a  condition  precedent  to  such  changes.  Ap- 
parently it  did  not  occur  to  me  as  needful  to  specify  this  iso- 
lation as  making  possible  the  differentiation  of  species;  since 
it  goes  without  saying  that  members  of  a  species  spreading 
east,  west,  north,  south,  and  forming  groups  hundreds  of 
miles  apart,  must,  while  breeding  with  those  of  the  same 
group  be  prevented  from  breeding  with  those  of  other  groups 
— prevented  from  having  their  locally-caused  modifications 
mutually  cancelled. 

The  importance  of  isolation  has  of  late  been  emphasized 
by  Dr.  Eomanes  and  others,  who,  to  that  isolation  conse- 
quent on  geographical  diffusion,  have  added  that  isolation 
which  results  from  difference  of  station  in  the  same  habitat, 
and  also  that  due  to  differences  in  the  breeding  periods 
arising  in  members  of  the  same  species.  Doubtless  in  what- 
ever way  effected,  the  isolation  of  a  group  subject  to  new 
conditions  and  in  course  of  being  changed,  is  requisite  as  a 
means  to  permanent  differentiation.  Doubtless  also,  as  con- 
tended by  Mr.  Gulick  and  Dr.  Eomanes,  there  is  a  difference 
between  the  case  in  which  an  entire  species  being  subject  to 
the  same  conditions  is  throughout  modified  in  character,  thus 
illustrating  what  Mr.  Gulick  calls  "  monotypic  evolution," 
and  the  case  in  which  different  parts  of  the  species,  leading 
different  lives,  will,  if  they  are  by  any  means  prevented  from 
inter-breeding  with  other  parts,  form  divergent  varieties: 
thus  illustrating  "  polytypic  evolution." 

§  174/.  Beyond  geographical  and  topographical  isolation, 
there  is  an  isolation  of  another  kind  regarded  by  some  as 
having  had  an  important  share  in  organic  evolution.  Fore- 
shadcwed  by  Mr.  Belt,  subsequently  enunciated  by  Mr.  Catch- 
pool,  fully  thought  out  by  Mr.  Gulick,  and  more  recently 
elaborated  by  Dr.  Eomanes,  "  Physiological  Selection  "  is  held 
to  account  for  the  genesis  of  marked  varieties  side  by  side 
with  their  parents.  It  is  contended  that  without  the  kind  of 
isolation  implied  by  it,  variations  will  be  swamped  by  inter- 


5 TO  THE  EVOLUTION  OP  LIFE. 

crossing,  and  divergence  prevented;  but  that  by  the  aid  of 
this  kind  of  isolation,  a  uniform  species  may  be  differentiated 
into  two  or  more  species,  though  its  members  continue  to  live 
in  the  same  area. 

Facts  are  assigned  to  show  that  slightly  unlike  varieties 
may  become  unable  to  inter-breed  either  with  the  parent- 
species  or  with  one  another.  This  mutual  inferiority  is  not 
of  the  kind  we  might  expect.  We  might  reasonably  suppose 
that  when  varieties  had  diverged  widely,  crossing  would  be 
impracticable,  because  their  constitutions  had  become  so  far 
unlike  as  to  form  an  unworkable  mixture.  But  there  seems 
evidence  that  the  infertility  arises  long  before  such  a  cause 
could  operate,  and  that  instead  of  failure  to  produce  a  work- 
able constitution,  there  is  failure  to  produce  any  constitution 
at  all — failure  to  fertilize.  Some  change  in  the  sexual 
system  is  suggested  as  accounting  for  this.  That  a  minute 
difference  in  the  reproductive  elements  may  suffice,  plants 
prove  by  the  fact  that  when  two  members  of  slightly-diver- 
gent varieties  are  fertilized  by  each  other's  pollen,  the  fer- 
tility is  less  than  if  each  were  fertilized  by  the  pollen  of  its 
own  variety;  and  where  the  two  kinds  of  pollen  are  both 
used,  that  derived  from  members  of  the  same  variety  is  pre- 
potent in  its  effect  over  that  derived  from  members  of  the 
other  variety. 

The  writers  above  named  contend  that  variations  must 
occur  in  the  reproductive  organs  as  well  as  in  other  organs ; 
that  such  variations  may  produce  relative  infertility  in  par- 
ticular directions;  and  that  such  relative  infertility  may  be 
the  first  step  towards  prevention  of  crossing  and  estab- 
lishment of  isolation:  so  making  possible  the  accumulation 
of  such  differences  as  mark  off  new  species.  Without  doubt 
we  have  here  a  legitimate  supposition  and  a  legitimate  infer- 
ence. Necessarily  there  must  happen  variations  of  the  kind 
alleged,  and  considering  how  sensitive  the  reproductive  sys- 
tem is  to  occult  influences  (witness  among  ourselves  the  fre- 
quent infertility  of  healthy  people  while  feeble  unhealthy 


RECENT  CRITICISMS  AND  HYPOTHESES.  571 

ones  are  fertile),  it  is  reasonable  to  infer  that  minute  and 
obscure  alterations  of  this  kind  may  make  slightly-different 
varieties  unable  to  inter-breed. 

Granting  that  there  goes  on  this  "  physiological  selection," 
we  must  recognize  it  as  one  among  the  causes  by  which  isola- 
tion is  produced,  and  the  differentiating  influence  of  natural 
selection  in  the  same  locality  made  possible. 

§  174</.  The  foregoing  criticisms  and  hypotheses  do  not, 
however,  affect  in  any  essential  way  the  pre-existing  concep- 
tions. If,  as  in  the  foregoing  chapters,  we  interpret  the  facts 
in  terms  of  that  redistribution  of  matter  and  motion  consti- 
tuting Evolution  at  large,  we  shall  see  that  the  general  theory, 
as  previously  held,  remains  outstanding. 

It  is  indisputable  that  to  maintain  its  life  an  organism 
must  maintain  the  moving  equilibrium  of  its  functions  in 
presence  of  environing  actions.  This  is  a  truism :  overthrow 
of  the  equilibrium  is  death.  It  is  a  corollary  that  when  the 
environment  is  changed,  the  equilibrium  of  functions  is  dis- 
turbed, and  there  must  follow  one  of  two  results — either  the 
equilibrium  is  overthrown  or  it  is  re-adjusted:  there  is  a 
re-equilibration.  Only  two  possible  ways  of  effecting  the 
re-adjustment  exist — the  direct  and  the  indirect.  In  the  one 
case  the  changed  outer  action  so  alters  the  moving  equili- 
brium as  to  call  forth  an  equivalent  reaction  which  balances 
it.  If  re-equilibration  is  not  thus  effected  in  the  individual 
it  is  effected  in  the  succession  of  individuals.  Either  the 
species  altogether  disappears,  or  else  there  disappear,  genera- 
tion after  generation,  those  members  of  it  the  equilibria  of 
whose  functions  are  least  congruous  with  the  changed  actions 
in  the  environment;  and  this  is  the  survival  of  the  fittest  or 
natural  selection. 

If  now  we  persist  in  thus  contemplating  the  problem  as  a 
statico-dynamical  one,  we  shall  see  that  much  of  the  discus- 
sion commonly  carried  on  is  beside  the  question.  The  centre 
around  which  the  collision  of  arguments  has  taken  place,  is 


572  THE  EVOLUTION  OP  LIFE. 

the  question  of  the  formation  of  species.  But  here  we  see 
that  this  question  is  a  secondary  and,  in  a  sense,  irrelevant 
one.  We  are  concerned  with  the  production  of  evolving  and 
diverging  organic  forms;  and  whether  these  are  or  are  not 
marked  off  by  so-called  specific  traits,  and  whether  they  will 
or  will  not  breed  together,  matters  little  to  the  general  argu- 
ment. If  two  divisions  of  a  species,  falling  into  unlike  con- 
ditions and  becoming  re-equilibrated  with  them,  eventually 
acquire  the  differences  of  nature  called  specific,  this  is  but  a 
collateral  result.  The  essential  result  is  the  formation  of 
divergent  organic  forms.  The  biologic  atmosphere,  so  to 
speak,  has  been  vitiated  by  the  conceptions  of  past  natural- 
ists, with  whom  the  identification  and  classification  of  species 
was  the  be-all  and  end-all  of  their  science,  and  who  regarded 
the  traits  which  enabled  them  to  mark  off  their  specimens 
from  one  another,  as  the  traits  of  cardinal  importance  in 
Nature.  But  after  ignoring  these  technical  ideas  it  becomes 
manifest  that  the  distinctions,  morphological  or  physiological, 
taken  as  tests  of  species,  are  merely  incidental  phenomena. 

Moreover,  on  continuing  thus  to  look  at  the  facts,  we  shall 
better  understand  the  relation  between  adaptive  and  specific 
characters,  and  between  specific  characters  and  those  many 
small  differences  which  always  accompany  them.  For  during 
re-equilibration  there  must,  beyond  those  changes  of  struc- 
ture required  to  balance  outer  actions  by  inner  actions,  be 
numerous  minor  changes.  In  any  complex  moving  equi- 
librium alterations  of  larger  elements  inevitably  cause  altera- 
tions of  elements  immediately  dependent  on  them,  and  these 
again  of  others:  the  effects  reverberate  and  re-reverberate 
throughout  the  entire  aggregate  of  actions  down  to  the  most 
minute.  Of  resulting  structural  changes  a  few  will  be  con- 
spicuous, more  will  be  less  conspicuous,  and  so  on  continu- 
ously multiplying  in  number  and  decreasing  in  amount. 

Here  seems  a  fit  place  for  remarking  that  there  are  certain 
processes  which  do  not  enter  into  these  re-equilibrations  but 
in  a  sense  interfere  with  them,  One  example  m.ust  suffice. 


RECENT  CRITICISMS  AND  HYPOTHESES.  573 

Among  dogs  may  be  observed  the  trick  of  rolling  on  some 
mass  having  a  strong  animal  smell:  commonly  a  decaying 
carcase.  This  trick  has  probably  been  derived  from  the  trick 
of  rolling  on  the  body  of  an  animal  caught  and  killed,  and 
so  gaining  a  tempting  odour.  A  male  dog  which  first  did 
this,  and  left  a  trail  apt  to  be  mistaken  for  that  of  prey, 
would  be  more  easily  found  by  a  female,  and  would  be  more 
likely  than  others  to  leave  posterity.  Now  such  a  trick 
could  have  no  relation  to  better  maintenance  of  the  moving 
equilibrium,  and  might  very  well  arise  in  a  dog  having  no 
superiority.  If  it  arose  in  one  of  the  worst  it  would  be 
eliminated  from  the  species,  but  if  it  arose  in  one  of  medium 
constitution,  fairly  capable  of  self-preservation,  it  would  tend 
to  produce  survival  of  certain  of  the  less  fit  rather  than  the 
fittest.  Probably  there  are  many  such  minor  traits  which  are 
in  a  sense  accidental,  and  are  neither  adaptive  nor  specific 
in  the  ordinary  sense. 

§  174/t.  But  now  let  it  be  confessed  that  though  all  pheno- 
mena of  organic  evolution  must  fall  within  the  lines  above 
indicated,  there  remain  many  unsolved  problems. 

Take  as  an  instance  the  descent  of  the  testes  in  the  Mam- 
malia. Neither  direct  nor  indirect  equilibration  accounts 
for  this.  We  cannot  consider  it  an  adaptive  change,  since 
there  seems  no  way  in  which  the  production  of  sperm-cells, 
internally  carried  on  in  a  bird,  is  made  external  by  adjust- 
ment to  the  changed  requirements  of  mammalian  life.  Nor 
can  we  ascribe  it  to  survival  of  the  fittest ;  for  it  is  incredible 
that  any  mammal  was  ever  advantaged  in  the  struggle  for 
life  by  this  changed  position  of  these  organs.  Contrariwise, 
the  removal  of  them  from  a  place  of  safety  to  a  place  of 
danger,  would  seem  to  be  negatived  by  natural  selection.  Nor 
can  we  regard  the  transposition  as  a  concomitant  of  re-equili- 
bration; since  it  can  hardly  be  due  to  some  change  in  the 
general  physiological  balance. 

An  example  of  another  order  is  furnished  by  the  mason- 


574  THE  EVOLUTION  OF  LIFE. 

wasp.  Several  instincts,  capacities,  peculiarities,  which  are 
in  a  sense  independent  though  they  cooperate  to  the  same 
end,  are  here  displayed.  There  is  the  instinct  to  build  a 
cell  of  grains  of  sand,  and  the  ability  to  do  this,  which  though 
in  a  sense  separate  may  be  regarded  as  an  accompaniment; 
and  there  is  the  secretion  of  a  cement — a  physiological  pro- 
cess not  directly  connected  with  the  psychological  process. 
After  oviposition  there  comes  into  play  the  instinct  to  seek, 
carry  home,  and  pack  into  the  cell,  the  small  caterpillars, 
spiders,  &c.,  which  are  to  serve  as  food  for  the  larva;  and 
then  there  is  the  instinct  to  sting  each  of  them  at  a  spot 
where  the  injected  hypnotic  poison  keeps  the  creature  insen- 
sible though  alive  till  it  is  wanted.  These  cannot  be  regarded 
as  parts  of  a  whole  developed  in  simultaneous  coordination. 
There  is  no  direct  connexion  between  the  building  instinct 
and  the  hypnotizing  instinct;  still  less  between  these  in- 
stincts and  the  associated  appliances.  What  were  the  early 
stages  they  passed  through  imagination  fails  to  suggest. 
Their  usefulness  depends  on  their  combination;  and  this 
combination  would  seem  to  have  been  useless  until  they  had 
all  reached  something  like  their  present  completeness.  Nor 
can  we  in  this  case  ascribe  anything  to  the  influence  of  teach- 
ing by  imitation,  supposed  to  explain  the  doings  of  social  in- 
sects ;  for  the  mason-wasp  is  solitary. 

Thus  the  process  of  organic  evolution  is  far  from  being 
fully  understood.  We  can  only  suppose  that  as  there  are 
devised  by  human  beings  many  puzzles  apparently  unan- 
swerable till  the  answer  is  given,  and  many  necromantic 
tricks  which  seem  impossible  till  the  mode  of  performance  is 
shown;  so  there  are  apparently  incomprehensible  results 
which  are  really  achieved  by  natural  processes.  Or,  other- 
wise, we  must  conclude  that  since  Life  itself  proves  to  be  in 
its  ultimate  nature  inconceivable,  there  is  probably  an  incon- 
ceivable element  in  its  ultimate  workings. 

END  or  VOL.  i. 


APPENDICES. 


APPENDIX    A. 


THE  GENERAL  LAW  OF  ANIMAL  FERTILITY. 

[In  the  Westminster  Review  for  April,  1852,  /  published  an 
essay  under  the  title  "  A  Theory  of  Population  deduced  from  the 
General  Law  of  Animal  fertility."  That  essay  was  the  germ  of 
Part  VI of  this  work,  "  The  Laws  of  Multiplication,"  in  which  its 
essential  theses  are  fully  developed.  When  developing  them,  I 
omitted  some  portions  of  the  original  essay — one  which  was  not  di- 
rectly relevant,  and  another  which  contained  a  speculation  open  to 
criticism.  As  indicated  in  §  74/,  I  find  that  this  speculation  has 
an  unexpected  congruity  with  recent  results  of  inquiry.  I  therefore 
decide  to  reproduce  it  here  along  with  the  definition  of  Life  pro- 
pounded in  that  essay,  which,  though  subsequently  replaced  by  the 
definition  elaborated  in  Part  I,  contains  an  element  of  truth.] 

Some  clear  idea  of  the  nature  of  Life  itself,  must,  indeed,  form 
a  needful  preliminary.  We  may  be  sure  that  a  search  for  the 
influences  determining  the  maintenance  and  multiplication  of 
living  organisms,  cannot  be  successfully  carried  out  unless  we 
understand  what  is  the  peculiar  property  of  a  living  organism — 
what  is  the  widest  generalization  of  the  phenomena  that  indicate 
life.  By  way  of  preparation,  therefore,  for  the  Theory  of  Popu- 
lation presently  to  be  developed,  we  propose  devoting  a  brief 
space  to  this  prior  question. 

***** 

Employing  the  term,  then,  in  its  usual  sense,  as  applicable  only 
to  organisms,  Life  may  be  defined  as — the  co-ordination  of  actions. 
The  growth  of  a  crystal,  which  is  the  highest  inorganic  process 
we  are  acquainted  with,  involves  but  one  action — that  of  accre- 
tion. The  growth  of  a  cell,  which  is  the  lowest  organic  process, 
involves  two  actions — accretion  and  disintegration — repair  and 
waste — assimilation  and  oxidation.  Wholly  deprive  a  cell  of 
oxygen,  and  it  becomes  inert — ceases  to  manifest  vital  phe- 
nomena ;  or,  as  we  say,  dies.  Give  it  no  .matter  to  assimilate, 
and  it  wastes  away  and  disappears,  from  continual  oxidation. 
Evidently,  then,  it  is  in  the  balance  of  these  two  actions  that  the 
life  consists.  It  is  not  in  the  assimilation  alone  ;  for  the  crystal 

577 


578  APPENDIX  A. 

assimilates  :  neither  is  it  in  the  oxidation  alone  ;  for  oxidation  is 
common  to  inorganic  matter  :  but  it  is  in  the  joint  maintenance 
of  these — the  co-ordination  of  them.  So  long  as  the  two  go  on 
together,  life  continues  :  suspend  either  of  them,  and  the  result 
is — death. 

The  attribute  which  thus  distinguishes  the  lowest  organic  from 
the  highest  inorganic  bodies,  similarly  distinguishes  the  higher 
organisms  from  the  lower  ones.  It  is  in  the  greater  complexity 
of  the  co-ordination — that  is,  in  the  greater  number  and  variety 
of  the  co-ordinated  actions — that  every  advance  in  the  scale  of 
being  essentially  consists.  And  whether  we  regard  the  numerous 
vital  processes  carried  on  in  a  creature  of  complex  structure  as  so 
many  additional  processes,  or  whether,  more  philosophically,  we 
regard  them  as  subdivisions  of  the  two  fundamental  ones — oxida- 
tion and  accretion — the  co-ordination  of  them  is  still  the  life. 
Thus  turning  to  what  is  physiologically  classified  as  the  vegetative 
system,  we  see  that  stomach,  lungs,  heart,  liver,  skin,  and  the 
rest,  must  work  in  concert.  If  one  of  them  does  too  much  or  too 
little — that  is,  if  the  co-ordination  be  imperfect — the  life  is  dis- 
turbed ;  and  if  one  of  them  ceases  to  act — that  is,  if  the  co-ordi- 
nation be  destroyed — the  life  is  destroyed.  So  likewise  is  it  with 
the  aninibl  system,  which  indirectly  assists  in  co-ordinating  the 
actions  of  the  viscera  by  supplying  food  and  oxygen.  Its  com- 
ponent parts,  the  limbs,  senses,  and  instruments  of  attack  or 
defence  must  perform  their  several  offices  in  proper  sequence ;  and 
further,  must  conjointly  minister  to  the  periodic  demands  of  the 
viscera,  that  these  may  in  turn  supply  blood.  How  completely 
the  several  attributes  of  animal  life  come  within  the  definition,  we 
shall  best  see  on  going  through  them  seriatim. 

Thus  Strength  results  from  the  co-ordination  of  actions ;  for  it 
is  produced  by  the  simultaneous  contraction  of  many  muscles  and 
many  fibres  of  each  muscle  ;  and  the  strength  is  great  in  propor- 
tion to  the  number  of  these  acting  together — that  is,  in  propor- 
tion to  the  co-ordination.  Swiftness  also,  depending  partly  on 
strength,  but  requiring  also  the  rapid  alternation  of  movements, 
equally  comes  under  the  expression ;  seeing  that,  other  things 
equal,  the  more  quickly  sequent  actions  can  be  made  to  follow 
each  other,  the  more  completely  are  they  co-ordinated.  So,  too, 
is  it  with  Agility  ;  the  power  of  a  chamois  to  spring  with  safety 
from  crag  to  crag  implies  accurate  co-ordination  in  the  movements 
of  many  different  muscles,  and  a  due  subordination  of  them  all  to 
the  perceptions.  The  definition  similarly  includes  Instinct,  which 
consists  in  the  uniform  succession  of  certain  actions  or  series  of 
actions  after  certain  sensations  or  groups  of  sensations  ;  and  that 
which  surprises  us  in  instinct  is  the  accuracy  with  which  these 
compound  actions  respond  to  these  compound  sensations  ;  that  is 


GENEEAL  LAW  OF  ANIMAL  FERTILITY.  579 

— the  completeness  of  their  co-ordination.  Thus,  likewise,  is  it 
with  Intelligence,  even  in  its  highest  manifestations.  That  which 
we  call  rationality  is  the  power  to  combine,  or  co-ordinate  a  great 
number  and  a  great  variety  of  complex  actions  for  the  achieve- 
ment of  a  desired  result.  The  husbandman  has  in  the  course  of 
years,  by  drainage  and  manuring,  to  bring  his  ground  into  a  fer- 
tile state ;  in  the  autumn  he  must  plough,  harrow,  and  sow,  for 
his  next  year's  crop ;  must  subsequently  hoe  and  weed,  keep  out 
cattle,  and  scare  away  birds ;  when  harvest  comes,  must  adapt 
the  mode  and  time  of  getting  in  his  produce  to  the  weather  and 
the  labour  market ;  he  must  afterwards  decide  when,  and  where, 
and  how  to  sell  to  the  best  advantage ;  and  must  do  all  this  that 
he  may  get  food  and  clothing  for  his  family.  By  properly  co- 
ordinating these  various  processes  (each  of  which  involves  many 
others) — by  choosing  right  modes,  right  times,  right  quantities, 
right  qualities,  and  performing  his  acts  in  right  order,  he  attains 
his  end.  But  if  he  have  done  too  little  of  this,  or  too  much  of 
that ;  or  have  done  one  thing  when  he  should  have  done  another 
— if  his  proceedings  have  been  badly  co-ordinated — that  is,  if  he 
have  lacked  intelligence — he  fails. 

We  find,  then,  that  the  co-ordination  of  actions  is  a  definition 
of  Life,  which  includes  alike  its  highest  and  its  lowest  manifesta- 
tions ;  and  not  only  so,  but  expresses  likewise  the  degree  of  Life, 
seeing  that  the  Life  is  high  in  proportion  as  the  co-ordination  is 
great.  Proceeding  upwards,  from  the  simplest  organic  cell  in 
which  there  are  but  two  interdependent  actions,  on  through  the 
group  in  which  many  such  cells  are  acting  in  concert,  on  through 
the  higher  group  in  which  some  of  these  cells  assume  mainly  the 
respiratory  and  others  the  assimilative  function — proceeding  still 
higher  to  organisms  in  which  these  two  functions  are  subdivided 
into  many  others,  and  in  which  some  cells  begin  to  act  together 
as  contractile  fibres;  next  to  organisms  in  which  the  visceral  divi- 
sion of  labour  is  carried  yet  further,  and  in  which  many  contrac- 
tile fibres  act  together  as  muscles — ascending  again  to  creatures 
that  combine  the  movements  of  several  limbs  and  many  bones 
and  muscles  in  one  action ;  and  further,  to  creatures  in  which 
complex  impressions  are  followed  by  the  complex  acts  we  term 
instinctive — and  arriving  finally  at  man,  in  whom  not  only  are 
the  separate  acts  complex,  but  who  achieves  his  ends  by  com- 
bining together  an  immense  number  and  variety  of  acts  often 
extending  through  years — we  see  that  the  progress  is  uniformly 
towards  greater  co-ordination  of  actions.  Moreover,  this  co-ordi- 
nation of  actions  unconsciously  constitutes  the  essence  of  our 
common  notion  of  life ;  for  we  shall  find,  on  inquiry,  that  when 
we  infer  the  death  of  an  animal,  which  does  not  move  on  being 
touched,  we  infer  it  because  we  miss  the  usual  co  ordination  of  a 


53$  APPESIHX  A. 


laere  lemaias  bat  to  aotke  the  objeetioa  wttdk  poaoiblT  may 
be  raised,  that  the  eo-oidiaatioa  of  aetioas  is  aot  fife,  bat  the 
Lack  of  sp.ee  forbids  gong  iato  this  at 
ft  mm*  smfiee  to  ayr  that  fife  aad  the  ability  to  man- 
tarn  fife  wffl  be  fond  the  same.  We  perpetually  expead  the 
vitality  we  hare  that  we  may  coatinme  oar  vitafity.  Our  power 

this  week  that  we  may  have  stoeagth  to  digest 
y  get  mote  food,  we  mart  ase  the  foiee  whkfc 
tike  food  we  hate  eatemgiivs  as.     E 


ia  dcaeodmir  fir  f>^ly  of  beiae,  or  ia 
of  am  iavafid,  we  ace  that  the  ebbia^  away  of  fife 

life,* 

[OBfro»Btf»wec«Bg~toie~itad  the  deftaitioa  of  Life 
of  thk  essay  with  the 
it  oeemr  to  • 

of  Life 


the  idea  of  eo-ordiaation  is  so  eaidi- 


aal  a  oae  that  it  afawld  be  expressed  mot  by 


iatha 

proper  pmtxv  for  the  first  part  of  this  work  k  already  stereotyped 
aadprimmt    Beias  nabfe  to  do  better  I  make  the  ameadmeat 


EC  of  oigamimmis  nbjeet  to  two 
Om  the  ome  hamd  by  aatanl  da 
mtk  of  i ood,  by  atMBpkcrie  dmmgn,  fe^  it 


GENERAL  LAW  OP  ANIMAL  FERTILITY.  581 

destroyed.  On  the  other  hand,  partly  bv  the  strength,  swiftness 
and  sagacity  of  its  members,  and  partly  by  their  fertility,  it  is 
constantly  being  maintained.  These  conflicting  sets  of  influences 
may  be  conveniently  generalized  as — the  forces  destructive  of 
race,  and  the  forces  preservative  of  race. 

§  2.  Whilst  any  race  continues  to  exist,  the  forces  destructive 
of  it  and  the  forces  preservative  of  it  must  perpetually  tend 
towards  equilibrium.  If  the  forces  destructive  of  it  decrease, 
the  race  must  gradually  become  more  numerous,  until,  either 
from  lack  of  food  or  from  increase  of  enemies,  the  destroying 
forces  again  balance  the  preserving  forces.  If,  reversely,  the 
forces  destructive  of  it  increase,  then  the  race  must  diminish, 
until,  either  from  its  food  becoming  relatively  more  abundant, 
or  from  its  enemies  dying  of  hunger,  the  destroying  forces  sink 
to  the  level  of  the  preserving  forces.  Should  the  destroying 
forces  be  of  a  kind  that  cannot  be  thus  met  (as  great  change  of 
climate),  the  race,  by  becoming  extinct,  is  removed  out  of  the 
category.  Hence  this  is  necessarily  the  law  of  maintenance  of  all 
races ;  seeing  that  when  they  cease  to  conform  to  it  they  cease  to  be. 

Now  the  forces  preservative  of  race  are  two — ability  in  each 
member  of  the  race  to  preserve  itself,  and  ability  to  produce 
other  members — power  to  maintain  individual  life,  and  power  to 
propagate  the  species.  These  must  vary  inversely.  When,  from 
lowness  of  organization,  the  ability  to  contend  with  external 
dangers  is  small,  there  must  be  great  fertility  to  compensate 
for  the  consequent  mortality ;  otherwise  the  race  must  die  out. 
When,  on  the  contrary,  high  endowments  give  much  capacity  of 
self-preservation,  there  needs  a  correspondingly  low  degree  of 
fertility.  Given  the  dangers  to  be  met  as  a  constant  quantity ; 
then,  as  the  ability  of  any  species  to  meet  them  must  be  a  con- 
stant quantity  too,  and  as  this  is  made  up  of  the  two  factors — 
power  to  maintain  individual  life  and  power  to  multiply — these 
cannot  do  other  than  vary  inversely. 

§  3.  To  show  that  observed  phenomena  harmonise  with  this 
a  priori  principle  seems  scarcely  needfuL  But,  though  axiomatic 
in  its  character,  and  therefore  incapable  of  being  rendered  more 
certain,  yet  illustrations  of  the  conformity  to  it  which  nature 
everywhere  exhibits,  will  facilitate  the  general  apprehension  of  it. 

In  the  vegetable  kingdom  we  find  that  the  species  consisting 
of  simple  cells,  exhibit  the  highest  reproductive  power.  The  yeast 
fungus,  which  in  a  few  hours  propagates  itself  throughout  a  large 
mass  of  wort,  offers  a  familiar  example  of  the  extreme  rapidity 
with  which  these  lowly  organisms  multiply.  In  the  Protocofc** 
nivalis,  a  microscopic  plant  which  in  the  course  of  a  night  reddens 


582  APPENDIX  A. 

many  square  miles  of  snow,  we  have  a  like  example ;  as  also  in 
the  minute  Algce,  which  colour  the  waters  of  stagnant  pools. 
The  sudden  appearance  of  green  films  on  damp  decaying  surfaces, 
the  spread  of  mould  over  stale  food,  and  the  rapid  destruction  of 
crops  by  mildew,  afford  further  instances.  If  we  ascend  a  step 
to  plants  of  appreciable  size,  we  still  find  that  in  proportion  as 
the  organization  is  low  the  fertility  is  great.  Thus  of  the  com- 
mon puff-ball,  which  is  little  more  than  a  mere  aggregation  of  cells, 
Fries  says,  "  in  a  single  individual  of  Reticularia  maxima,  I  have 
counted  (calculated  ?)  10,000,000  sporules."  From  this  point 
upwards,  increase  of  bulk  and  greater  complexity  of  structure 
are  still  accompanied  by  diminished  reproductive  power ;  instance 
the  Macrocystis  pyrifera,  a  gigantic  sea-weed,  which  sometimes 
attains  a  length  of  1500  feet,  of  which  Carpenter  remarks,  "  This 
development  of  the  nutritive  surface  takes  place  at  the  expense 
of  the  fructifying  apparatus,  which  is  here  quite  subordinate."  * 
And  when  we  arrive  at  the  highly-organized  exogenous  trees,  we 
find  that  not  only  are  they  many  years  before  beginning  to  bear 
with  any  abundance,  but  that  even  then  they  produce,  at  the  out- 
side, but  a  few  thousand  seeds  in  a  twelvemonth.  During  its 
centuries  of  existence,  an  oak  does  not  develop  as  many  acorns  as 
a  fungus  does  spores  in  a  single  night. 

Still  more  clearly  is  this  truth  illustrated  throughout  the 
animal  kingdom.  Though  not  so  great  as  the  fertility  of  the 
Protophyta,  which,  as  Prof.  Henslow  says,  in  some  cases  passes 
comprehension,  the  fertility  of  the  Protozoa  is  yet  almost  beyond 
belief.  In  the  polygastric  animalcules  spontaneous  fission  takes 
place  so  rapidly  that  "  it  has  been  calculated  by  Prof.  Ehren- 
berg  that  no  fewer  than  268  millions  might  be  produced  in  a 
month  from  a  single  Paramecium  /  "  \  and  even  this  astonishing 
rate  of  increase  is  far  exceeded  in  another  species,  one  individual 
of  which,  "  only  to  be  perceived  by  means  of  a  high  magnifying 
power,  is  calculated  to  generate  170  billions  in  four  days."  J 
Amongst  the  larger  organisms  exhibiting  this  lowest  mode  of 
reproduction  under  a  modified  form — that  of  gemmation — we 
see  that,  though  not  nearly  so  rapid  as  in  the  Infusoria,  the  rate 
of  multiplication  is  still  extremely  high.  This  fact  is  well  illus- 
trated by  the  polypes ;  and  in  the  apparent  suddenness  with 
which  whole  districts  are  blighted  by  the  Aphis  (multiplying  by 
internal  gemmation),  we  have  a  familiar  instance  of  the  startling 
results  which  the  parthenogenetic  process  can  achieve.  Where 
reproduction  becomes  occasional  instead  of  continuous,  as  it  does 
amongst  higher  creatures,  the  fertility  equally  bears  an  inverse 
ratio  to  the  development.  "  The  queen  ant  of  the  African 

. *  Prin..of  Phys..  2nd  edit.,  p.  77.  f  Hid.,  3rd  edit.,  p  249. 

J  Ibid.,  p.  124. 


GENERAL  LAW  OP  ANIMAL  FERTILITY.  583 

Termites  lays  80,000  eggs  in  twenty-four  hours  ;  and  the  common 
hair  worm  (Grordius)  as  many  as  8,000,000  in  less  than  one  day."  * 
Amongst  the  Vertebrata  the  lowest  are  still  the  most  prolific. 
"  It  has  been  calculated,"  says  Carpenter,  "  that  above  a  million 
of  eggs  are  produced  at  once  by  a  single  codfish."  j  In  the 
strong  and  sagacious  shark  comparatively  few  are  found.  Still  less 
fertile  are  the  higher  reptiles.  And  amongst  the  Mammalia, 
beginning  with  small  Rodents,  which  quickly  reach  maturity, 
produce  large  litters,  and  several  litters  in  the  year ;  advancing 
step  by  step  to  the  higher  mammals,  some  of  which  are  long  in 
attaining  the  reproductive  age,  others  of  which  produce  but  one 
litter  in  a  year,  others  but  one  young  one  at  a  time,  others  who 
uaite  these  peculiarities;  and  ending  with  the  elephant  and  man, 
the  least  prolific  of  all,  we  find  that  throughout  this  class,  as 
throughout  the  rest,  ability  to  multiply  decreases  as  ability  to 
maintain  individual  life  increases. 

§  4.  The  a  priori  principle  thus  exemplified  has  an  obverse  of 
a  like  axiomatic  character.  We  have  seen  that  for  the  continu- 
ance of  any  race  of  organisms  it  is  needful  that  the  power  of  self- 
preservation  and  the  power  of  reproduction  should  vary  inversely. 

We  shall  now  see  that,  quite  irrespective  of  such  an  end  to  be 
subserved,  these  powers  could  not  do  otherwise  than  vary  in- 
versely. In  the  nature  of  things  species  can  subsist  only  by  con- 
forming to  this  law ;  and  equally  in  the  nature  of  things  they  can- 
not help  conforming  to  it. 

Reproduction,  under  all  its  forms,  may  be  described  as  the 
separation  of  portions  of  a  parent  plant  or  animal  for  the  purpose 
of  forming  other  plants  or  animals.  Whether  it  be  by  sponta- 
neous fission,  by  gemmation,  or  by  gemmules ;  whether  the 
detached  products  be  bulbels,  spores  or  seeds,  ovisacs,  ova  or 
spermatozoa ;  or  however  the  process  of  multiplication  be  modi- 
fied, it  essentially  consists  in  the  throwing  off  of  parts  of  adult 
organisms  for  the  purpose  of  making  new  organisms.  On  the 
other  hand,  self  preservation  is  fundamentally  a  maintenance  of 
the  organism  in  undiminished  bulk.  Amongst  the  lowest  forms 
of  life,  aggregation  of  tissue  is  the  only  mode  in  which  the  self- 
preserving  power  is  shown.  Even  in  the  highest,  sustaining  the 
body  in  its  integrity  is  that  in  which  self-preservation  most  truly 
consists — is  the  end  which  the  widest  intelligence  is  indirectly 
made  to  subserve.  Whilst,  on  the  one  side,  it  cannot  be  denied 
that  the  increase  of  tissue  constituting  growth  is  self-preservation 
both  in  essence  and  in  result ;  neither  can  it,  on  the  other  side, 
be  denied  that  a  diminution  of  tissue,  either  from  injury,  disease, 
or  old  age,  is  in  both  essence  and  result  the  reverse. 

*  A^rassiz  and  Gould,  p.  274.  f  Prin.  of  Phys.,  3rd  edit.,  p.  964. 


584  APPENDIX  A. 

Hence  the  maintenance  of  the  individual  and  the  propagation 
of  the  race  being  respectively  aggregative  and  separative,  necessarily 
vary  inversely.  Every  generative  product  is  a  deduction  from 
the  parental  life;  and,  as  already  pointed  out,  to  diminish  life  is 
to  diminish  the  ability  to  preserve  life.  The  portion  thrown  off 
is  organised  matter;  vital  force  has  been  expended  in  the  organ- 
isation of  it,  and  in  the  assimilation  of  its  component  elements ; 
which  vital  force,  had  no  such  portion  been  made  and  thrown  off, 
would  have  been  available  for  the  preservation  of  the  parent. 

Neither  of  these  forces,  therefore,  can  increase,  save  at  the 
expense  of  the  other.  The  one  draws  in  and  incorporates  new 
material ;  the  other  throws  off  material  previously  incorporated. 
The  one  adds  to ;  the  other  takes  from.  Using  a  convenient 
expression  for  describing  the  facts  (though  one  that  must  not  be 
construed  into  an  hypothesis),  we  may  say  that  the  force  which 
builds  up  and  repairs  the  individual  is  an  attractive  force,  whilst 
that  which  throws  off  germs  is  a  repulsive  force.  But  whatever  may 
turn  out  to  be  the  true  nature  of  the  two  processes,  it  is  clear  that 
they  are  mutually  destructive ;  or,  stating  the  proposition  in  its 
briefest  form — Individuation  and  Reproduction  are  antagonistic. 

Again,  illustrating  the  abstract  by  reference  to  the  concrete, 
let  us  now  trace  throughout  the  organic  world  the  various  phases 
of  this  antagonism. 

§  5.  All  the  lowest  animal  and  vegetable  forms — Protozoa  and 
Protophyta — consist  essentially  of  a  single  cell  containing  fluid, 
and  having  usually  a  solid  nucleus.  This  is  true  of  the  Infu- 
soria, the  simplest  Entozoa,  and  the  microscopic  Algae  and  Fungi. 
The  organisms  so  constituted  uniformly  multiply  by  spontaneous 
fission.  The  nucleus,  originally  spherical,  becomes  elongated, 
then  constricted  across  its  smallest  diameter,  and  ultimately 
separates,  when  "  its  divisions,"  says  Prof.  Owen,  describing  the 
process  in  the  Infusoria,  "  seem  to  repel  each  other  to  positions 
equidistant  from  each  othe>,  and  from  the  pole  or  end  of  the 
body  to  which  they  are  nearest.  The  influence  of  these  distinct 
centres  of  assimilation  is  to  divert  the  flow  of  the  plasmatic  fluid 
from  a  common  course  through  the  body  of  the  polygastrian  to 
two  special  courses  about  those  centres.  So  much  of  the  primary 
developmental  process  is  renewed,  as  leads  to  the  insulation  of 
the  sphere  of  the  influence  of  each  assimilative  centre  from  that 
of  the  other  by  the  progressive  formation  of  a  double  party  wall 
of  integument,  attended  by  progressive  separation  of  one  party 
wall  from  the  other,  and  by  concomitant  constriction  of  the  body 
of  the  polygastrian,  until  the  vibratile  action  of  the  superficial 
cilia  of  each  separating  moiety  severs  the  narrowed  neck  of 
union,  and  they  become  two  distinct  individuals."  *  Similar  in 
*  "  Parthenogenesis,"  p.  8. 


GENERAL  LAW  OF  ANIMAL  FERTILITY.  585 

its  general  view  is  Dr.  Carpenter's  description  of  the  multiplica- 
tion of  vegetable  cells,  which  he  says  divide,  "  in  virtue,  it  may 
be  surmised,  of  a  sort  of  mutual  repulsion  between  the  two 
halves  of  the  endochrome  (coloured  cell-contents)  which  leads  to 
their  spontaneous  separation."  *  Under  a  modified  form  of  this 
process,  the  cell-contents,  instead  of  undergoing  bisection,  divide 
into  numerous  parts,  each  of  which  ultimately  becomes  a  separate 
individual.  In  some  of  the  Algae  "  a  whole  brood  of  young  cells 
may  thus  be  at  once  generated  in  the  cavity  of  the  parent-cell, 
which  subsequently  bursts  and  sets  them  free."  f  The  Achlya 
prolifera  multiplies  after  this  fashion.  Amongst  the  Fungi,  too, 
the  same  mode  of  increase  is  exemplified  by  the  Protococcus  nivalis. 
And  "  it  would  appear  that  certain  Infusoria,  especially  the 
Kolpodince,  propagate  by  the  breaking-up  of  their  own  mass  into 
reproductive  particles."  J 

Now  in  this  fissiparous  mode  of  multiplication,  which  "is 
amazingly  productive,  and  indeed  surpasses  in  fertility  any  other 
with  which  we  are  acquainted,"  §  we  see  most  clearly  the  anta- 
gonism between  individuation  and  reproduction.  We  see  that 
the  reproductive  process  involves  destruction  of  the  individual ; 
for  in  becoming  two,  the  parent  fungus  or  polygastrian  must  be 
held  to  lose  its  own  proper  existence ;  and  when  it  breaks  up 
into  a  numerous  progeny,  does  so  still  more  completely.  More- 
over, this  rapid  mode  of  multiplication  not  only  destroys  the  in- 
dividuals in  whom  it  takes  place,  but  also  involves  that  their  in- 
dividualities, whilst  they  continue,  shall  be  of  the  lowest  kind. 
For  assume  a  protozoon  to  be  growing  by  imbibition  at  a  given 
rate,  and  it  follows  that  the  oftener  it  divides  the  smaller  must 
be  the  size  it  attains  to  ;  that  is,  the  smaller  the  development  of 
its  individuality.  And  a  further  manifestation  of  the  same  truth 
is  seen  in  the  fact  that  the  more  frequent  the  spontaneous  fission 
the  shorter  the  existence  of  each  individual.  So  that  alike  by 
preventing  anything  beyond  a  microscopic  bulk  being  attained,  by 
preventing  the  continuance  of  this  in  its  integrity  beyond  a  few 
hours,  and  by  be,  tig  fatal  when  it  occurs,  this  most  active  mode  of 
reproduction  shows  the  strongest  antagonism  to  individual  life. 

§  6.  Whether  or  not  we  regard  reproduction  as  resulting  from 
a  repulsive  force  (and,  as  seen  above,  both  Owen  and  Carpenter 
lean  to  some  such  view),  and  whether  or  not  we  consider  the 
formation  of  the  individual  as  due  to  the  reverse  of  this — an 
attractive  force — we  cannot,  on  studying  the  phenomena,  help 
admitting  that  two  opposite  activities  thus  generalized  are  at 

*  Prin.  ofPhys.,  p.  92.  f  Ibid.,  p.  fl3.  f  Ibid.,  p.  91 T. 

§  "  A  General  Outline  of  the  Animal  Kingdom."  By  Prof.  T.  R.  Jones, 
F  G.  S,p.  G1.. 


586  APPENDIX  A. 

work ;  we  cannot  help  admitting  that  the  aggregative  and  sepa- 
rative tendencies  do  in  each  case  determine  the  respective  de- 
velopments of  the  individual  and  the  race.  On  ascending  one 
degree  in  the  scale  of  organic  life,  we  shall  find  this  truth  clearly 
exemplified. 

For  if  these  single-celled  organisms  which  multiply  so  rapidly 
be  supposed  to  lose  some  of  their  separative  tendency,  what 
must  be  the  result  ?  They  now  not  only  divide  frequently,  but 
the  divided  portions  fly  apart.  How,  then,  will  a  diminution  of 
this  separative  tendency  first  show  itself  ?  May  we  not  expect 
that  it  will  show  itself  in  the  divided  portions  not  flying  apart, 
but  remaining  near  each  other,  and  forming  a  group  ?.  This  we 
find  in  nature  to  be  the  first  step  in  advance.  The  lowest  com- 
pound organisms  are  "  simple  aggregations  of  vesicles  without  any 
definite  arrangement,  sometimes  united,  but  capable  of  existing  sepa- 
rately." *  In  these  cases,  "  every  component  cell  of  the  aggre- 
gate mass  that  springs  from  a  single  germ,  being  capable  of 
existing  independently  of  the  rest,  may  be  regarded  as  a  distinct 
individual."  f  The  several  stages  of  this  aggregation  are  very 
clearly  seen  in  both  the  animal  and  vegetable  kingdoms.  In  the 
HcBtnatococcus  binalis,  the  plant  producing  the  reddish  slime  seen 
on  damp  surfaces,  not  only  does  each  of  the  cells  retain  its 
original  sphericity,  but  each  is  separated  from  its  neighbour  by  a 
wide  interval  filled  with  mucus ;  so  that  it  is  only  as  being 
diffused  through  a  mass  of  mucus  common  to  them  all,  that  these 
cells  can  be  held  to  constitute  one  individual.  We  find,  too,  that 
"the  component  cells,  even  in  the  highest  Algae,  are  generally 
separated  from  each  other  by  a  large  quantity  of  mucilaginous 
intercellular  substance."  J  And,  again,  the  tissue  of  the  simpler 
Lichens,  "  in  consequence  of  the  very  slight  adhesion  of  its 
component  cells,  is  said  to  be  pulverulent."  §  Similarly  the 
Protozoa,  by  their  feeble  union,  constitute  the  organisms  next 
above  them.  Amongst  the  Polygastrica  there  are  many  casos 
"  in  which  the  individuals  produced  by  fission  or  gemmation  do 
not  become  completely  detached  from  each  other."  ||  The  Oph- 
rydium,  for  instance,  "  exists  under  the  form  of  a  motionless  jelly- 
like  mass  .  .  .  made  up  of  millions  of  distinct  and  similar 
individuals  imbedded  in  a  gelatinous  connecting  substance  ;  "  *[ 
and  again,  the  Uvella,  or  "  grape  monad,"  consists  of  a  cluster 
"which  strongly  resembles  a  transparent  mulberry  rolling  itself 
across  the  field  of  view  by  the  ciliary  action  of  its  component 
individuals."  **  The  parenchyma  of  the  Sponge,  too,  is  made 

*  Carpenter.  f  Prin.  of  Phys.,  p.  873. 

±  Ibid,  p.  203.  $  Ibid.,  p.  209. 

I  Ibid.,  p.  249.  f  Ibid.,  p.  249. 

**  Ibid.,  p.  250. 


GENERAL  LAW  OF  ANIMAL   FERTILITY.  587 

up  of  cells  "  each  of  which  has  the  character  of  a  distinct  ani- 
malcule, having  a  certain  power  of  spontaneous  motion,  obtaining 
and  assimilating  its  own  food,  and  altogether  living  by  and  for 
itself ;  "  and  so  small  is  the  cohesion  of  these  individual  cells, 
that  the  tissue  they  constitute  "  drains  away  when  the  mass  is 
removed  from  the  water,  like  white  of  egg."  * 

Of  course  in  proportion  as  the  aggregate  tendency  leading  to 
the  formation  of  these  groups  of  monads  is  strong,  we  may 
expect  that,  other  things  equal,  the  groups  will  be  large. 
Proceeding  upwards  from  the  yeast  fungus,  whose  cells  hold 
together  in  groups  of  four,  five,  and  six,f  there  must  be  found 
in  each  species  of  these  composite  organisms  a  size  of  group 
determined  by  the  strength  of  the  aggregative  tendency  in  that 
species.  Hence  we  may  expect  that,  when  this  limit  is  passed, 
the  group  no  longer  remains  united,  but  divides.  Such  we  find 
to  be  the  fact.  These  groups  of  cells  undergo  the  same  process 
that  the  cells  themselves  do.  They  increase  up  to  a  certain 
point,  and  then  multiply  either  by  simple  spontaneous  fission  or 
by  that  modification  of  it  called  gemmation.  The  Volvox  globator, 
which  is  made  up  of  a  number  of  monads  associated  together  in 
the  form  of  a  hollow  sphere,  develops  within  itself  a  number  of 
smaller  spheres  similarly  constituted ;  and  after  these,  swimming 
freely  in  its  interior,  have  reached  a  certain  size,  the  parent 
group  of  animalcules  bursts  and  sets  the  interior  groups  free. 
And  here  we  may  observe  how  this  compound  individuality  of 
the  Volvox  is  destroyed  in  the  act  of  reproduction  as  the  simple 
individuality  of  the  monad  is.  Again,  in  the  higher  forms  of 
grouped  cells,  where  something  like  organisation  begins  to  show 
itself,  the  aggregations  are  not  only  larger,  but  the  separative 
process,  now  carried  on  by  the  method  of  gemmation,  no  longer 
wholly  destroys  the  individual.  And  in  fact,  this  gemmation 
may  be  regarded  as  the  form  which  spontaneous  fission  must 
assume  in  ceasing  to  be  fatal ;  seeing  that  gemmation  essentially 
consists  in  the  separation,  not  into  halves,  but  into  a  larger  part 
and  a  smaller  part ;  the  larger  part  continuing  to  represent  the 
original  individual.  Thus  in  the  common  Hydra  or  fresh-water 
polype,  "  little  bud-like  processes  are  developed  from  the  external 
surface,  which  are  soon  observed  to  resemble  the  parent  in 
character,  possessing  a  digestive  sac,  mouth,  and  tentacula ;  for 
a  long  time,  however,  their  cavity  is  connected  with  that  of  the 
parent ;  but  at  last  the  communication  is  cut  off,  and  the  young 
polype  quits  its  attachment,  and  goes  in  quest  of  its  own  main- 
tenance." \ 

§  7.  Progress  from  these  forms  of  organisation  to  still  higher 
*  Prin.  of  Phy*.,  p.  256.  f  ^"*>  P-  212.  \  Ibid.,  p.  266. 


588  APPENDIX  A. 

forms  is  similarly  characterized  by  increase  of  the  aggregative 
tendency  or  diminution  of  the  separative,  and  similarly,  exhibits 
the  necessary  antagonism  between  the  development  of  the  in- 
dividual and  the  increase  of  the  race.  That  process  of  grouping 
which  constitutes  the  first  step  towards  the  production  of  complex 
organisms,  we  shall  now  find  repeated  in  the  formation  of  series 
of  groups.  Just  as  a  diminution  of  the  separative  tendency  is 
shown  in  the  aggregation  of  divided  monads,  so  is  a  further 
diminution  of  it  shown  in  the  aggregation  of  the  divided  groups 
of  monads.  The  first  instance  that  occurs  is  afforded  by  the 
compound  polypes.  "  Some  of  the  simpler  forms  of  the  com- 
posite ffydroida,"  says  Carpenter,  "  may  be  likened  to  a  ffydra, 
whose  gemmae,  instead  of  becoming  detached,  remain  perma- 
nently connected  with  the  parent ;  and  as  these  in  their  turn  may 
develop  gemmae  from  their  own  bodies,  a  structure  of  more  or 
less  arborescent  character  may  be  produced."  *  A  similar  species 
of  combination  is  observable  amongst  the  Bryozoa,  and  the  com- 
pound Tunicata.  Every  degree  of  union  may  be  found  amongst 
these  associated  organisms ;  from  the  one  extreme  in  which 
the  individuals  can  exist  as  well  apart  as  together,  to  the  other 
extreme  in  which  the  individuals  are  lost  in  the  general  mass. 
Whilst  each  Bryozoon  is  tolerably  independent  of  its  neighbour, 
"in  the  compound  ffydroida,  the  lives  of  the  polypes  are  sub- 
ordinate to  that  of  the  polypdom."  f  Of  the  Salpidce  and 
Pyrosomidce,  Carpenter  says  : — "  Although  closely  attached  to  one 
another,  these  associated  animals  are  capable  of  being  separated 
by  a  smart  shock  applied  to  the  sides  of  the  vessel  in  which  they 
are  swimming.  ...  In  other  species,  however,  the  sepa- 
rate animals  are  imbedded  in  a  gelatinous  mass,"  and  in  one 
kind  "  there  is  an  absolute  union  between  the  vascular  systems 
of  the  different  individuals."  \ 

In  the  same  manner  that  with  a  given  aggregative  tendency 
there  is  a  limit  to  the  size  of  groups,  so  is  there  a  similarly- 
determined  limit  to  the  size  of  series  of  groups ;  and  that 
spontaneous  fission  which  we  have  seen  in  cells  and  groups  of 
cells  we  here  find  repeated.  In  the  lower  Annelida,  for  example, 
"  after  the  number  of  segments  in  the  body  has  been  greatly 
multiplied  by  gemmation,  a  separation  of  those  of  the  posterior 
portion  begins  to  take  place  ;  a  constriction  forms  itself  about  the 
beginning  of  the  posterior  third  of  the  body,  in  front  of  which 
the  alimentary  canal  undergoes  a  dilatation,  whilst  on  the  seg- 
ment behind  it  a  proboscis  and  eyes  are  developed,  so  as  to  form 
the  head  of  the  young  animal  which  is  to  be  budded  off ;  and  in 
due  time,  by  the  narrowing  of  the  constriction,  a  complete  sepa- 

*  Prin.  o/Phys.,  p.  267.  f  Ibid.,  p.  276. 

j  Jbid.,  2nd  edit,  p.  116. 


GENERAL  LAW  OP  ANIMAL  FERTILITY.  589 

ration  is  effected."  *  Not  ^infrequently  in  the  Nais  this  process  is 
repeated  in  the  young  one  before  it  becomes  independent  of  the 
parent.  The  higher  Annelida  are  distinguished  by  the  greater 
number  of  segments  held  in  continuity  ;  an  obvious  result  of 
comparatively  infrequent  fission.  In  the  class  Myriapoda,  which 
stands  next  above,  "  there  is  no  known  instance  of  multiplication 
by  fission."  f  Yet  even  here  the  law  may  be  traced  both  in  the 
number  and  structure  of  the  segments.  The  length  of  the  body 
is  still  increased  after  birth  "  by  gemmation  from  (or  partial 
fission  of)  the  penultimate  segment."  The  lower  members  of  the 
class  are  distinguished  from  the  higher  by  the  greater  extent  to 
which  this  gemmation  is  carried.  Moreover,  the  growing  aggre- 
gative tendency  is  seen  in  the  fact,  that  each  segment  of  the  Julus 
"  is  formed  by  the  coalescence  of  two  original  segments,"  J  whilst 
in  the  Scolopendridce,  which  are  the  highest  of  this  class,  "  the 
head,  according  to  Mr.  Newport,  is  composed  of  eight  segments, 
which  are  often  consolidated  into  one  piece ; "  §  both  of  which 
phenomena  may  be  understood  as  arrests  of  that  process  of  fission, 
which,  if  allowed  to  go  a  little  further,  would  have  produced  dis- 
tinct segments ;  and,  if  allowed  to  go  further  still,  would  have 
separated  these  segments  into  groups. 

§  8.  Remarking,  first,  how  gradually  this  mode  of  multiplica- 
tion disappears — how  there  are  some  creatures  that  spontaneously 
divide  or  not  according  to  circumstances ;  others  that  divide 
when  in  danger  (the  several  parts  being  capable  of  growing  into 
complete  individuals)  ;  others  which,  though  not  self-dividing,  can 
live  on  in  each  half  if  artificially  divided ;  and  others  in  which 
only  one  of  the  divided  halves  can  live — how,  again,  in  the  Crus- 
taceans the  power  is  limited  to  the  reproduction  of  lost  limbs ; 
how  there  are  certain  reptiles  that  can  re-supply  a  lost  tail,  but 
only  imperfectly;  and  how  amongst  the  higher  Vertebrate  the 
ability  to  repair  small  injuries  is  all  that  remains — remarking  thus 
much,  let  us  now,  by  way  of  preparation  for  what  is  to  follow, 
consider  the  significance  of  the  foregoing  facts  taken  in  connec- 
tion with  the  definition  of  Life  awhile  since  given. 

This  spontaneous  fission,  which  we  have  seen  to  be,  in  all 
cases,  more  or  less  destructive  of  individual  life,  is  simply  a 
cessation  in  the  co-ordination  of  actions.  From  the  single  cell, 
the  halves  of  whose  nucleus,  instead  of  continuing  to  act  together, 
begin  to  repel  each  other,  fly  apart,  establish  distinct  centres  of 
assimilation,  and  finally  cause  the  cell  to  divide ;  up  to  the  Anne- 
lidan,  whose  string  of  segments  separates,  after  reaching  a  certain 
length ;  we  everywhere  see  the  phenomenon  to  be  fundamentally 

*  Prin.  of  /%«.,  p.  954.  f  Ibid.,  p.  958. 

J  Hid ,  p.  688.  §  Ibid.,  p.  958. 


590  APPENDIX  A. 

this.  The  tendency  to  separate  is  the  tendency  not  to  act 
together,  probably  arising  from  inability  to  act  together  any 
longer ;  and  the  process  of  separation  is  the  process  of  ceasing  to 
act  together.  How  truly  non-co-ordination  is  the  essence  of  the 
matter  will  be  seen  on  observing  that  fission  takes  place  more  or 
less  rapidly,  according' as  the  co-ordinating  apparatus  is  less  or 
more  developed.  Thus,  "  the  capability  of  spontaneous  division 
is  one  of  the  most  distinctive  attributes  of  the  acrite  type  of 
structure ;"  *  the  acrite  type  of  structure  being  that  in  which  the 
neurine  or  nervous  matter  is  supposed  to  be  diffused  through  the 
tissues  in  a  molecular  state,  and  in  which,  therefore,  there  exists 
no  distinct  nervous  or  co-ordinating  system.  From  this  point 
upwards  the  gradual  disappearance  of  spontaneous  fission  is 
clearly  related  to  the  gradual  appearance  of  nerves  and  ganglia — 
a  fact  well  exemplified  by  tha  several  grades  of  Annelida  and 
Myriapoda.  And  when  we  remember  that  in  the  embryotic 
development  of  these  classes,  the  nervous  system  does  not  make 
its  appearance  until  after  the  rest  of  the  organism  has  made 
great  progress,  we  may  even  suspect  that  that  coalescence  of 
segments  characteristic  of  the  Myriapoda,  exhibits  the  co  ordi- 
nating  power  of  the  rapidly -growing  nervous  system  overtaking 
and  arresting  the  separative  tendency ;  and  doing  this  most 
where  it  (the  nervous  system)  is  most  developed,  namely,  in  the 
head. 

And  here  let  us  remark,  in  passing,  how,  from  this  point  of 
view,  we  still  more  clearly  discern  the  antagonism  of  individuation 
and  reproduction.  We  before  saw  that  the  propagation  of  the 
race  is  at  the  expense  of  the  individual :  in  the  above  facts  we  may 
contemplate  the  obverse  of  this — may  sec  that  the  formation  of 
the  individual  is  at  the  expense  of  the  race.  This  combination  of 
parts  that  are  tending  to  separate  and  become  distinct  beings — 
this  union  of  many  incipient  minor  individualities  into  one  large 
individuality — is  an  arrest  of  reproduction — a  diminution  in  the 
number  produced.  Either  these  units  may  part  and  lead  inde- 
pendent lives,  or  they  may  remain  together  and  have  their  actions 
co-ordinated.  Either  they  may,  by  their  diffusion,  form  a  small, 
simple,  and  prolific  race,  or,  by  their  aggregation,  a  large,  com- 
plex, and  infertile  one.  But  manifestly  the  aggregation  involves 
the  infertility ;  and  the  fertility  involves  the  smallness. 

§  9.  The  ability  to  multiply  by  spontaneous  fission,  and  the 
ability  to  maintain  individual  life,  are  opposed  in  yet  another 
mode.  It  is  not  in  respect  of  size  only,  but  still  more  in  respect 
of  structure,  that  the  antagonism  exists. 

*  "  A  Gcr-crai  I>ut?ac  of  the  Animal  Kingdom."  By  Professor  T.  R. 
Jones,  p.  01. 


GENERAL  LAW  OP  ANIMAL  FERTILITY.  591 

Higher  organisms  arc  distinguished  from  lower  ones  partly  by 
bulk,  and  partly  by  complexity.  This  complexity  essentially 
consists  in  the  mutual  dependence  of  numerous  different  organs, 
each  subserving  the  lives  of  the  rest,  and  each  living  by  the  help 
of  the  rest.  Instead  of  being  made  up  of  many  like  parts,  per- 
forming like  functions,  as  the  Crinoid,  the  Star-fish,  or  the  Milli- 
pede, a  vertebrate  animal  is  made  up  of  many  unlike  parts, 
performing  unlike  functions.  From  that  initial  form  of  a  com- 
pound organism,  in  which  a  number  of  minor  individuals  are 
simply  grouped  together,  we  may,  more  or  less  distinctly,  trace 
not  only  the  increasing  closeness  of  their  union,  and  the  gradual 
disappearance  of  their  individualities  in  that  of  the  mass,  but 
the  gradual  assumption  by  them  of  special  duties.  And  this 
"  physiological  division  of  labour,"  as  it  has  been  termed,  has 
the  same  effect  as  the  division  of  labour  amongst  men.  As  the 
preservation  of  a  number  of  persons  is  better  secured  when, 
uniting  into  a  society,  they  severally  undertake  different  kinds 
of  work,  than  when  they  are  separate  and  each  performs  for  him- 
self every  kind  of  work  ;  so  the  preservation  of  a  congeries  of 
parts,  which,  combining  into  one  organism,  respectively  assume 
nutrition,  respiration,  circulation,  locomotion,  as  separate  func- 
tions, is  better  secured  than  when  those  parts  are  independent, 
and  each  fulfils  for  itself  all  these  functions. 

But  the  condition  under  which  this  increased  ability  to  main- 
tain life  becomes  possible  is,  that  the  parts  shall  cease  to  separate. 
While  they  are  perpetually  separating,  ijt  is  clear  that  they  cannot 
assume  mutually  subservient  duties.  And  it  is  further  clear  that 
the  more  the  tendency  to  separate  diminishes,  that  is,  the  larger 
the  groups  that  remain  connected,  the  more  minutely  and  perfectly 
can  that  subdivision  of  functions  which  we  call  organization  be  car- 
ried out. 

Thus  we  see  that  in  its  most  active  form  the  ability  to  multiply 
is  antagonistic  to  the  ability  to  maintain  individual  life,  not  only 
as  preventing  increase  of  bulk,  but  also  as  preventing  organiza- 
tion— not  only  as  preventing  homogeneous  co-ordination,  but  as 
preventing  heterogeneous  co-ordination. 

§  10.  To  establish  the  unbroken  continuity  of  this  law  cf 
fertility,  it  will  be  needful,  before  tracing  its  results  amongst  the 
higher  animals,  to  explain  in  what  manner  spontaneous  fission  is 
now  understood,  and  what  the  cessation  of  it  essentially  mean?. 
Originally,  naturalists  supposed  that  creatures  which  multiply  by 
self-division,  under  any  of  its  several  forms,  continue  so  to 
multiply  perpetually.  In  many  cases,  however,  it  has  latterly 
been  shown  that  they  do  not  do  this ;  and  it  is  now  becoming  a 
received  opinion  that  they  do  not,  and  cannot,  do  this,  in  any 


502  APPENDIX  A. 

case.  A  fertilised  germ  appears  here,  as  amongst  higher  organ- 
isms, to  be  the  point  of  departure  ;  and  that  constant  formation 
of  new  tissue  implied  in  the  production  of  a  great  number  of 
individuals  by  fission,  seems  gradually  to  exhaust  the  germinal 
capacity  in  the  same  way  that  the  constant  formation  of  new 
tissue,  during  the  development  of  a  single  mammal,  exhausts  it. 
The  phenomena  classified  by  Steenstrup  as  "  Alternate  Genera- 
tion," and  since  generalised  by  Professor  Owen  in  his  work  "  On 
Parthenogenesis,"  illustrate  this.  The  egg  of  a  Medusa  (jelly- 
fish) develops  into  a  polypoid  animal  called  the  Strobila.  This 
Strobila  lives  as  the  polype  does,  and,  like  it,  multiplies  rapidly 
by  gemmation.  After  a  great  number  of  individuals  has  been 
thus  produced,  and  when,  as  we  must  suppose,  the  germinal 
capacity  is  approaching  exhaustion,  each  Strobila  begins  to  exhibit 
a  series  of  constrictions,  giving  it  some  resemblance  to  a  rouleau 
of  coin  or  a  pile  of  saucers.  These  constrictions  deepen;  the 
segments  gradually  develop  tentacula ;  the  terminal  segment 
finally  separates  itself,  and  swims  away  in  the  form  of  a  young 
Medusa ;  the  other  segments,  in  succession,  do  the  same ;  and 
from  the  eggs  which  these  Medusae,  produce,  other  like  series  of 
polypoid  animals,  multiplying  by  gemmation,  originate.  In  the 
compound  Polypes,  in  the  Tunicata,  in  the  Trematoda,  and  in  the 
Aphis,  we  find  repeated,  under  various  modifications,  the  same 
phenomenon. 

Understanding  then,  this  lowest  and  most  rapid  mode  of 
multiplication  to  consist  essentially  in  the  production  of  a  great 
number  of  individuals  from  a  single  germ — perceiving,  further, 
that  diminished  activity  of  this  mode  of  multiplication  consists 
essentially  in  the  aggregation  of  the  germ-product  into  larger 
masses — and  seeing,  lastly,  that  the  disappearance  of  this  mode 
of  multiplication  consists  essentially  in  the  aggregation  of  the 
germ-product  into  one  mass — we  shall  be  in  apposition  to  com- 
prehend, amongst  the  higher  animals,  that  new  aspect  of  the  law, 
under  which  increased  individuation  still  involves  diminished 
reproduction.  Progressing  from  those  lowest  forms  of  life  in 
which  a  single  ovum  originates  countless  organisms,  through 
the  successive  stages  in  which  the  number  of  organisms  so 
originated  becomes  smaller  and  smaller ;  and  finally  arriving 
at  a  stage  in  which  one  ovum  produces  but  one  organism ;  we 
have  now,  in  our  further  ascent,  to  observe  the  modified  mode 
in  which  this  same  necessary  antagonism  between  the  ability 
to  multiply,  and  the  ability  to  preserve  individual  life,  is  ex- 
hibited. 

§11.  Throughout  both  the  animal  and  vegetable  kingdoms, 
3-; aeration  is  effected  "by  the  union  of  the  contents  of  a 


-GENERAL  LAW  OF  ANIMAL  FERTILITY.  593 

'  sperm-cell '  with  those  of  a  '  germ-cell ;  '  the  latter  being  that 
from  within  which  the  embryo  is  evolved,  whilst  the  former 
supplies  some  material  or  influence  necessary  to  its  evolution."  * 
Amongst  the  lowest  vegetable  organisms,  as  in  the  Desmidece, 
the  Diatomacece,  and  other  families  of  the  inferior  Algce,  these 
cells  do  not  appreciably  differ ;  and  the  application  to  them  of 
the  terms  "  sperm-cell  "  and  "  germ-cell  "  is  hypothetical.  From 
this  point  upwards,  however,  distinctions  become  visible.  As 
we  advance  to  higher  and  higher  types  of  structure,  marked 
differences  arise  in  the  character  of  these  cells,  in  the  organs 
evolving  them,  and  in  the  position  of  these  organs,  which  are 
finally  located  in  separate  sexes.  Doubtless  a  separation  in  the 
functions  of  "  sperm-cell "  and  "  germ-cell  "  has  simultaneously 
arisen.  That  change  from  homogeneity  of  function  to  hetero- 
geneity of  function  which  essentially  constitutes  progress  in 
organization  may  be  assumed  to  take  place  here  also ;  and, 
indeed,  it  is  probable  that  the  distinction  gradually  established 
between  these  cells,  in  origin  and  appearance,  is  merely  significant 
of,  and  consequent  upon,  the  distinction  that  has  arisen  between 
them  in  constitution  and  office.  Let  us  now  inquire  in  what  this 
distinction  consists. 

If  the  foundation  of  every  new  organism  be  laid  by  the  com- 
bination of  two  elements,  we  may  reasonably  suspect  that  these 
two  elements  are  typical  of  some  two  fundamental  divisions  of 
which  the  new  organism  is  to  consist.  As  nothing  in  nature 
is  without  meaning  and  purpose,  we  may  be  sure  that  the 
universality  of  this  binary  origin,  signifies  the  universality  of  a 
binary  structure.  The  simplest  and  broadest  division  of  which 
an  organism  is  capable  must  be  that  signified.  What,  then, 
must  this  division  be  ? 

The  proposed  definition  of  organic  life  supplies  an  answer. 
If  organic  life  be  the  co-ordination  of  actions,  then  an  organism 
may  be  primarily  divided  into  parts  whose  actions  are  co-ordi- 
nated, and  parts  which  co-ordinate  them — organs  which  are 
made  to  work  in  concert,  and  the  apparatus  which  makes  them 
so  work — or,  in  other  words,  the  assimilative,  vascular,  excretory, 
•and  muscular  systems  on  the  one  hand,  and  the  nervous  system 
on  the  other.  The  justness  of  this  classification  will  become 
further  apparent,  when  it  is  remembered  that  by  the  nervous 
system  alone  is  the  individuality  established.  By  it  all  parts  are 
made  one  in  purpose,  instead  of  separate ;  by  it  the  organism  is 
rendered  a  conscious  whole — is  enabled  to  recognise  its  own 
extent  and  limits ;  and  by  it  are  all  injuries  notified,  repairs 
directed,  and  the  general  conservation  secured.  The  more  the 
nervous  system  is  developed,  the  more  reciprocally  subservient  do 
*  Prin.  of  Phys.,  p.  907. 


594  APPENDIX  A. 

the  components  of  the  b»dy  become — the  less  can  they  bcr.r 
separating.  And  that  which  thus  individuates  many  parts  into 
one  whole,  must  be  considered  as  more  broadly  distinguished 
from  the  parts  individuated,  than  any  of  these  parts  from  each 
other.  Further  evidence  in  support  of  this  position  may  be 
drawn  from  the  fact,  that  as  we  ascend  in  the  scale  of  animal  life, 
that  is,  as  the  co-ordination  of  actions  becomes  greater,  we  find 
the  co-ordinating  or  nervous  system  becoming  more  and  more 
definitely  separated  from  the  rest ;  and  in  the  vertebrate  or 
highest  type  of  structure  we  find  the  division  above  insisted  on 
distinctly  marked.  The  co-ordinating  parts  and  the  parts  co- 
ordinated are  placed  on  opposite  sides  of  the  vertebral  column. 
With  the  exception  of  a  few  ganglia,  the  whole  of  the  nervous 
masses  are  contained  within  the  neural  arches  of  the  vertebrae  ; 
whilst  all  the  viscera  and  limbs  are  contained  within,  or  appended 
to,  the  haemal  arches — the  terms  neural  and  haemal  having,  in- 
deed, been  chosen  to  express  this  fundamental  division. 

If,  then,  there  be  truth  in  the  assumption  that  the  two 
elements,  which,  by  their  union,  give  origin  to  a  new  organism, 
typify  the  two  essential  constituents  of  such  new  organism,  we 
must  infer  that  the  sperm-cell  and  germ-cell  respectively  consist 
of  co-ordinating  matter  and  matter  to  be  co-ordinated — neurine 
and  nutriment.  That  apparent  identity  of  sperm-cell  and  germ- 
cell  seen  in  the  lowest  forms  of  life  may  thus  be  understood  as 
significant  to  the  fact  that  no  extended  co-ordination  of  actions 
exists  in  the  generative  product — each  cell  being  a  separate  indi- 
vidual ;  and  the  dissimilarity  seen  in  higher  organic  types  may, 
conversely,  be  understood  as  expressive  of,  and  consequent  upon, 
the  increasing  degree  of  co-ordination  exhibited."  * 

That  the  sperm-cell  and  germ-cell  are  thus  contrasted  in 
nature  and  function  may  further  be  suspected  on  considering 
the  distinctive  characteristics  of  the  sexes.  Of  the  two  elements 
they  respectively  contribute  to  the  formation  of  a  fertile  germ,  it 
may  be  reasonabjy  supposed  that  each  furnishes  that  which  it 
possesses  in  greatest  abundance  and  can  best  spare.  Well,  in 
the  greater  size  of  the  nervous  centres  in  the  male,  as  well  as  in 
the  fact  that  during  famines  men  succumb  sooner  than  women, 
we  see  that  in  the  male  the  co-ordinating  system  is  relatively 
predominant.  From  the  same  evidence,  as  well  as  from  the 
greater  abundance  of  the  cellular  and  adipose  tissues  in  women, 
we  may  infer  that  the  nutritive  system  predominates  in  the 
female,  f  Here,  then,  is  additional  support  for  the  hypothesis 

*  Should  it  be  objected  that  in  the  higher  plants  the  sperm  cell  and  germ- 
cell  differ,  though  no  distinct  co-ordinating  system  exists,  it  is  replied  that 
there  is  co  ordination  of  actions,  though  of  a  feeble  kind,  and  that  there  must 
be  some  agency  by  which  this  is  carried  on. 

f  It  is  a  significant  fact  that  amongst  the  diu-cious  invertebrata,  where  the 


GENERAL  LAW  OF  ANIMAL  FERTILITY.  595 

tli at  the  sperm-cell,  which  is  supplied  by  tne  male,  contains  co- 
ordinating matter,  and  the  germ-cell,  which  is  supplied  by  the 
female,  contains  matter  to  be  co-ordinated. 

The  same  inference  may,  again,  be  drawn  from  a  general  view 
of  the  maternal  function.  For  if,  as  we  see,  it  is  the  office  of 
the  mother  to  afford  milk  to  the  infant,  and  during  a  previous 
period  to  afford  blood  to  the  foetus,  it  becomes  probable  that 
during  a  yet  earlier  stage  it  is  still  the  function  to  supply  nutri- 
ment, though  in  another  form.  Indeed  when,  ascending  gradually 
the  scale  of  animal  life,  we  perceive  that  this  supplying  of  milk, 
and  before  that  of  blood,  is  simply  £  continuation  of  the  previous 
process,  we  may  be  sure  that,  with  Nature's  usual  consistency, 
this  process  is  essentially  one  from  the  beginning. 

Quite  in  harmony  with  this  hypothesis  concerning  the  respec- 
tive natures  of  the  sperm-cell  and  germ-cell  is  a  remark  of  Car- 
penter's on  the  same  point: — 

"  Looking,"  he  says,  "  to  the  very  equal  mode  in  which  the  characters  of 
the  two  parents  are  mingled  in  hybrid  offspring,  and  to  the  certainty  that  the 
material  conditions  which  determine  the  development  of  the  germ  are  almost 
exclusively  female,  it  would  seem  probable  that  the  dynamical  conditions 
iu  great  part,  furnished  by  the  ma 


ly  female,  it  would  seem  probable  that  the  dynamical  conditions  are, 
,le."  * 


§  12.  Could  nothing  but  the  foregoing  indirect  evidence  be 
adduced  in  proof  of  the  proposition  that  the  spermatozoon  is 
essentially  a  neural  element,  and  the  ovum  essentially  a  haemal 
element,  we  should  scarcely  claim  for  it  anything  more  than 
plausibility.  On  finding,  however,  that  this  indirect  evidence  is 
merely  introductory  to  evidence  of  a  quite  direct  nature,  its 
significance  will  become  apparent.  Adding  to  their  weight 
taken  separately  the  force  of  their  mutual  confirmation,  these 
two  series  of  proofs  will  be  seen  to  give  the  hypothesis  a  high 
degree  of  probability.  The  direct  evidence  now  to  be  considered 
is  of  several  kinds. 

On  referring  to  the  description  of  the  process  of  multiplication 
in  monads,  quoted  some  pages  back  (§  5),  from  Professor  Owen, 
the  reader  will  perceive  that  it  is  by  the  pellucid  nucleus  that  the 
growth  and  reproduction  of  these  single-celled  creatures  are  regu- 
lated. The  nucleus  controls  the  circulation  of  the  plasmatic 
fluid ;  the  fission  of  the  nucleus  is  the  first  step  towards  the 
formation  of  another  cell ;  each  half  of  the  divided  nucleus  estab- 
lishes round  itself  an  independent  current ;  and,  apparently,  it  is 
by  the  repulsion  of  the  nuclei  that  the  separation  into  two  indi- 

mitritive  system  greatly  exceeds  the  other  systems  in  development,  the  female 
is  commonly  the  largest,  and  often  greatly  so.     In  some  of  the  Rotifera  the 
i;i:ile  has  no  nutritive  system  at  all.     See  Prin.  of  Phi/s..  p.  954 
*  Prin.  ofPhys.,  p.  908. 


59G 


APPENDIX  A. 


viduals  is  finally  effected.  All  which  facts,  when  generalised, 
imply  that  the  nucleus  is  the  governing  or  co-ordinating  part. 
Now,  Professor  Owen  subsequently  points  out  that  the  matter  of 
the  sperm-cell  performs  in  the  fertilised  germ-cell  just  this  same 
function  which  the  nucleus  performs  in  a  single-celled  animal. 
We  find  the  absorption  by  a  germ-cell  of  the  contents  of  a  sperm- 
cell  "followed  by  the  appearance  of 'a  pellucid  nucleus  in  the 
centre  of  the  opaque  and  altered  germ-cell ;  we  further  see  its 
successive  fissions  governed  by  the  preliminary  division  of  the 
pellucid  centre ; "  and,  led  by  these  and  other  facts,  Professor 
Owen  thinks  that  "one  cannot  reasonably  suppose  that  the 
nature  and  properties  of  the  nucleus  of  the  impregnated  germ-cell 
and  that  of  the  monad  can  be  different."  *  And  hence  he  further 
infers  that  "  the  nucleus  of  the  monad  is  of  a  nature  similar  to,  if 
not  identical  with,"  the  matter  of  the  spermatozoon.  But  we 
have  seen  that  in  the  monad  the  nucleus  is  the  co-ordinating  part ; 
and  hence  to  say  that  the  sperm-cell  is,  in  nature,  identical  with 
it,  is  to  say  that  the  sperm-cell  consists  of  co-ordinating  matter. 

Chemical  analysis  affords  further  evidence,  though,  from  the 
imperfect  data  at  present  obtained,  less  conclusive  evidence  than 
could  be  wished.  Partly  from  the  white  and  gray  nervous  sub- 
stances having  been  analysed  together  instead  of  separately,  and 
partly  from  the  difficulty  of  isolating  the  efficient  contents  of  the 
sperm-cells,  a  satisfactory  comparison  cannot  be  made.  Never- 
theless, possessing  in  common,  as  they  do,  one  element,  by  which 
they  are  specially  characterised,  the  analysis,  as  far  as  it  goes, 
supports  our  argument.  The  following  table,  which  has  been 
made  up  from  data  given  in  the  Cyclopaedia  of  Anatomy  and  Physi- 
ology, Art.  NERVOUS  SYSTEM,  gives  the  proportion  of  this  ele- 
ment in  the  brain  in  different  conditions,  and  shows  how  impor- 
tant is  its  presence. 


In 

In 

In 

In 

In 

Infants. 

Youth. 

Adults. 

Old  Men. 

Idiots. 

Solid  constituents  in  a  hundred 

parts  of  brain 

17.21 

25.74 

27.49 

26.15 

29.07 

Of  these  solid  constituents    the 

phosphorus  amounts  to  

0.8 

1.65 

1.80 

1.00 

0.85 

Which   gives    a    percentage   of 

phosphorus  in  the  solid  con- 

stituents of  

4.65 

6.41 

6.54 

3.82 

2.92 

This  connection  between  the  quantity  of  phosphorus  present 
and  the  degree  of  mental  power  exhibited,  is  sufficiently  signifi- 

*  "  Parthenogenesis,"  pp.  66,  67. 


GENERAL  LAW  OF  ANIMAL  FERTILITY.  597 

cant;  and  the  fact  that  in  the  same  individual  the  varying 
degrees  of  cerebral  activity  are  indicated  by  the  varying  quanti- 
ties of  alkaline  phosphates  excreted  by  the  kidneys,*  still  more 
clearly  shows  the  essentialness  of  phosphorus  as  a  constituent  of 
nervous  matter.  Respecting  the  constitution  of  sperm-cells 
chemists  do  not  altogether  agree.  One  thing,  however,  is  certain 
— that  they  contain  unoxidized  phosphorus;  and  also  a  fatty 
acid,  that  is  not  improbably  similar  to  the  fatty  acid  contained  in 
neurine.f  In  fact,  there  would  seem  to  be  present  the  con- 
stituents of  that  oleophosphoric  acid  which  forms  so  distinctive 
an  element  of  the  brain.  That  a  large  quantity  of  binoxide  of 
protein  is  also  present,  may  be  ascribed  to  the  fact  that  a  great 
part  of  the  sperm-cell  consists  merely  of  the  protective  membrane 
and  its  locomotive  appendage ;  the  really  efficient  portion  being 
but  the  central  contents.^ 

Evidence  of  a  more  conclusive  nature — evidence,  too,  which 
will  show  in  what  direction  our  argument  tends — is  seen  in  the 
marked  antagonism  of  the  nervous  and  generative  systems. 
Thus,  the  fact  that  intense  mental  application,  involving  great 
waste  of  the  nervous  tissues,  and  a  corresponding  consumption  of 
nervous  matter  for  their  repair,  is  accompanied  by  a  cessation  in 
the  production  of  sperm-cells,  gives  strong  support  to  the  hypo- 
thesis that  the  sperm-cells  consist  essentially  of  neurine.  And 
this  becomes  yet  clearer  on  finding  that  the  converse  fact  is  true 
— that  undue  production  of  sperm-cells  involves  cerebral  inac- 
tivity. The  first  result  of  a  morbid  excess  in  this  direction  is 
headache,  which  may  be  taken  to  indicate  that  the  brain  is  out  of 
repair ;  this  is  followed  by  stupidity  ;  should  the  disorder  con- 
tinue, imbecility  supervenes,  ending  occasionally  in  insanity. 

That  the  sperm-cell  is  co-ordinating  matter,  and  the  germ- 
cell  matter  to  be  co-ordinated,  is,  therefore,  an  hypothesis  not 
only  having  much  a  priori  probability,  but  one  supported  by  nu- 
merous facts. 

§  13.  This  hypothesis  alike  explains,  and  is  confirmed  by,  the 
truth,  that  throughout  the  vertebrate  tribes  the  degree  of  fertility 
varies  inversely  as  the  development  of  the  nervous  system. 

*  "Lectures  on  Animal  Chemistry."  By  Dr.  Bence  Jones.  Medical 
Times,  Sept.  18th,  1851.  See  also  Prin.  of  Phys.,  p.  171. 

\  Cyclopaedia  of  Anatomy  and  Physiology,  Vol.  IV,  p.  506. 

j  From  a  remark  of  Drs.  Wagner  and  Leuckart  this  chemical  evidence 
seems  to  have  already  suggested  the  idea  that  the  sperm-cell  becomes 
"metamorphosed  into  the  central  parts  of  the  nervous  system."  But 
though  they  reject  this  assumption,  and  though  the  experiments  of  Mr. 
Newport  clearly  render  it  untenable,  yet  none  of  the  facts  latterly  brought  to 
lijlht  conflict  with  the  hypothesis  that  the  sperm-cell  contains  unorganized 
co-ordinating  matter. 
39 


598  APPENDIX  A. 

The  necessary  antagonism  of  Individuation  and  Reproduction 
does  indeed  show  itself  amongst  the  higher  animals,  in  some 
degree  in  the  manner  hitherto  traced ;  namely,  as  determining 
the  total  bulk.  Though  the  parts  now  thrown  off,  being  no 
longer  segments  or  gemmae,  are  not  obvious  diminutions  of  the 
parent,  yet  they  must  be  really  such.  Under  the  form  of  in- 
ternal fission,  the  separative  tendency  is  as  much  opposed  to  the 
aggregative  tendency  as  ever  ;  and,  other  things  equal,  the  greater 
or  less  development  of  the  individual  depends  upon  the  less  or 
greater  production  of  new  individuals  or  germs  of  new  indi- 
viduals. As  in  groups  of  cells,  and  series  of  groups  of  cells,  we 
saw  that  there  was  in  each  species  a  limit,  passing  which,  the 
germ  product  would  not  remain  united ;  so  in  each  species  of 
higher  animal  there  is  a  limit,  passing  which,  the  process  of  cell- 
multiplication  results  in  the  throwing  off  of  cells,  instead  of  re- 
sulting in  the  formation  of  more  tissue.  Hence,  taking  an  aver- 
age view,  we  see  why  the  smaller  animals  so  soon  arrive  at  a 
reproductive  age,  and  produce  large  and  frequent  broods  ;  and 
why,  conversely,  increased  size  is  accompanied  by  retarded  and 
diminished  fertility. 

But,  as  above  implied,  it  is  not  so  much  to  the  bulk  of  the 
body  as  a  whole,  as  to  the  bulk  of  the  nervous  system,  that 
fertility  stands  related  amongst  the  higher  animals.  Probably, 
indeed,  it  stands  thus  related  in  all  cases  ;  the  difference  simply 
arising  from  the  fact,  that  whereas  in  the  lower  organisms,  where 
the  nervous  system  is  not  concentrated,  its  bulk  varies  as  the 
bulk  of  the  body,  in  the  higher  organisms  it  does  not  do  so.  Be 
this  as  it  may,  however,  we  see  clearly  that,  amongst  the  verte- 
brata,  the  bodily  development  is  not  the  determining  circum- 
stance. In  a  fish,  a  reptile,  a  bird,  and  a  mammal  cf  the  same 
weight,  there  is  nothing  like  equality  of  fecundity.  Cattle  and 
horses,  arriving  as  they  do  so  soon  at  a  reproductive  age,  are 
much  more  prolific  than  the  human  race,  at  the  same  time  that 
they  are  much  larger.  And  whilst,  again,  the  difference  in  size 
between  the  elephant  and  man  is  far  greater,  their  respective 
powers  of  multiplication  are  less  unlike.  Looking  in  these  cases 
at  the  nervous  systems,  however,  we  find  no  such  discrepancy. 
On  learning  that  the  average  ratio  of  the  brain  to  the  body  is — 
in  fishes,  1  to  5668  ;  in  reptiles,  1  to  1321  ;  in  birds,  1  to  212  ; 
and  in  mammals,  1  to  186  ;  *  their  different  degrees  of  fecundity 
are  accounted  for.  Though  an  ox  will  outweigh  half-a-dozen 
men,  yet  its  brain  and  spinal  cord  are  far  less  than  those  of  one 
man ;  and  though  in  bodily  development  the  elephant  so  im- 
mensely exceeds  the  human  being,  yet  the  elephant's  cerebro- 
spinal  system  is  o'nly  thrice  the  size  attained  by  that  of  civilized 
*  Quain's  Elements  of  Anatomy,  p.  672. 


GENERAL  LAW  OF  ANIMAL  FERTILITY.  599 

men.*  Unfortunately,  it  is  impossible  to  trace  throughout  the 
animal  kingdom  this  inverse  relationship  between  the  nervous 
and  reproductive  systems  with  any  accuracy.  Partly  from  the 
fact  that,  in  each  case,  the  degree  of  fertility  depends  on  three 
variable  elements — the  age  at  which  reproduction  begins,  the 
number  produced  at  a  birth,  and  the  frequency  of  the  births; 
partly  from  the  fact  that,  in  respect  to  most  animals,  these  data 
are  not  satisfactorily  attainable,  and  that,  when  they  are  attain- 
able, they  are  vitiated  by  the  influence  of  domesticity  ;  and  parti v 
from  the  fact  that  no  precise  measurement  of  the  respective 
nervous  systems  has  been  made,  we  are  unable  to  draw  any  but 
general  and  somewhat  vague  comparisons.  These,  however,  as 
far  as  they  go,  are  in  our  favour.  Ascending  from  beings  of  the 
acrite  nerveless  type,  which  are  the  most  prolific  of  all,  through 
the  various  invertebrate  sub-kingdoms,  amongst  which  spontane- 
ous fission  disappears  as  the  nervous  system  becomes  developed ; 
passing  again  to  the  least  nervous  and  most  fertile  of  the  verte- 
brate series — Fishes,  of  which,  too,  the  comparatively  large- 
brained  cartilaginous  kinds  multiply  much  less  rapidly  than  the 
others ;  progressing  through  the  more  highly  endowed  and  less 
prolific  Reptiles  to  the  Mammalia,  amongst  which  the  Rodents, 
with  their  unconvoluted  brains,  are  noted  for  their  fecundity  ;  and 
ending  with  man  and  the  elephant,  the  least  fertile  and  largest- 
brained  of  all — there  seems  to  be  throughout  a  constant  relation- 
ship between  these  attributes. 

And  indeed,  on  turning  back  to  our  a  priori  principle,  no  other 
relationship  appears  possible.  We  found  it  to  be  the  necessary 
law  of  maintenance  of  races,  that  the  ability  to  maintain  indi- 
vidual life  and  the  ability  to  multiply  vary  inversely.  But  the 
ability  to  maintain  individual  life  is  in  all  cases  measured  by  the 
development  of  the  nervous  system.  If  it  be  in  good  visceral  organi- 
zation that  the  power  of  self-preservation  is  shown,  this  implies 
some  corresponding  nervous  apparatus  to  secure  sufficient  food. 
If  it  be  in  strength,  there  must  be  a  provision  of  nerves  and 
nervous  centres  answering  to  the  number  and  size  of  the  muscles. 
If  it  be  in  swiftness  and  agility,  a  proportionate  development  of 
the  cerebellum  is  presupposed.  If  it  be  in  intelligence,  this  varies 

*  The  maximum  weight  of  the  horse's  brain  is  1  Ib.  7  ozs. ;  the  human 
brain  weighs  3  Ibs.,  and  occasionally  as  much  as  4  Ibs. ;  the  brain  of  a 
whale,  75  feet  long,  weighed  5  Ibs.  5  ozs. ;  and  the  elephant's  brain  reaches 
from  8  Ibs.  to  10  Ibs.  Of  the  whale's  fertility  we  know  nothing;  but  the 
elephant's  quite  agrees  with  the  hypothesis.  The  elephant  does  not  attain  its 
full  size  until  it  is  thirty  years  old,  from  which  we  may  infer  that  it  arrives 
at  a  reproductive  age  later  than  man  does ;  its  period  of  gestation  is  two 
years,  and  it  produces  one  at  a  birth.  Evidently,  therefore,  it  is  much  loss 
prolific  than  man.  Sec  MiillerV  I'hi/slology  (Baly's  translation),  p.  815,  and 
Quain's  Elements  of  Anatomy,  p.  071. 


600  APPENDIX  A. 

with  the  size  of  the  cerebrum.  As  in  all  cases  co-ordination  of 
actions  constitutes  the  life,  or,  what  is  the  same  thing,  the  ability 
to  maintain  life ;  and  as  throughout  the  animal  kingdom  this  co- 
ordination, under  all  its  forms,  is  effected  by  nervous  agents  of 
some  kind  or  other ;  and  as  each  of  these  nervous  agents  per- 
forms but  one  function ;  it  follows  that  in  proportion  to  the 
number  of  the  actions  co-ordinated  must  be  the  number  of 
nervous  agents.  Hence  the  nervous  system  becomes  the  universal 
measure  of  the  degree  of  co-ordination  of  actions;  that  is,  of  the 
life,  or  ability  to  maintain  life.  And  if  the  nervous  system  varies 
directly  as  the  ability  to  maintain  life,  it  must  vary  inversely  as 
the  ability  to  multiply.* 

And  here,  assuming  the  constitution  of  the  sperm-cell  above 
inferred  to  be  the  true  one,  we  see  how  the  obverse  a  priori  prin- 
ciple is  fulfilled.  Where,  as  amongst  the  lowest  organisms,  bulk 
is  expressive  of  life,  the  antagonism  of  individuation  and  re- 
production was  broadly  exhibited  in  the  fact  that  the  making  of 
two  or  more  new  individuals  was  the  wnmaking  of  the  original 
individual.  And  now,  amongst  the  higher  organisms,  where  bulk 
is  no  longer  the  measure  of  life,  we  see  that  this  antagonism  is 
between  the  neural  elements  thrown  off,  and  that  internal  neural 
mass  whose  bulk  is  the  measure  of  life.  The  production  of  co- 
ordinating cells  must  be  at  the  expense  of  the  co-ordinating  appa- 
ratus ;  and  the  aggregation  of  the  co-ordinating  apparatus  must 
be  at  the  expense  of  co-ordinating  cells.  How  the  antagonism 
affects  the  female  economy  is  not  so  clear.  Possibly  the  provision 
required  to  be  made  for  supplying  nervous  as  well  as  other  nutri- 
ment to  the  embryo,  involves  an  arrest  in  the  development  of  the 
nervous  system  ;  and  if  so,  probably  this  arrest  takes  place  early 
in  proportion  as  the  number  of  the  coming  offspring  makes  the 
required  provision  great :  or  rather,  to  put  the  facts  in  their  right 
sequence,  an  early  arrest  renders  the  production  of  a  numerous 
offspring  possible. 

§  14.  The  law  which  we  have  thus  traced  throughout  the  ani- 

*  That  the  size  of  the  nervous  system  is  the  measure  of  the  ability  to 
maintain  life,  is  a  proposition  that  must,  however,  be  taken  with  some 
qualifications.  The  ratio  between  the  amounts  of  gray  and  white  matter 
present  in  each  case  is  probably  a  circumstance  of  moment.  Moreover,  the 
temperature  of  the  blood  may  have  a  modifying  influence ;  seeing  that  small 
nervous  centres  exposed  to  rapid  oxidation  will  be  equivalent  to  larger  ones 
more  slowly  oxidized.  Indeed,  we  see  amongst  mankind,  that  though,  in 
the  main,  size  of  brain  determines  mental  power,  yet  temperament  exercises 
some  control.  There  is  reason  to  think,  too,  that  certain  kinds  of  nervous 
action  involve  greater  consumption  of  nervous  tissue  than  others ;  and  this 
will  somewhat  complicate  the  comparisons.  Nevertheless,  these  admissions 
do  not  affect  the  generalization  as  a  whole,  but  merely  prepare  us  to  meet 
with  minor  irregularities. 


GENERAL  LAW  OP  ANIMAL  FERTILITY.  601 

mal  kingdom,  and  which  must  alike  determine  the  different  fer- 
tilities of  different  species,  and  the  variations  of  fertility  in  the 
same  species,  we  have  now  to  consider  in  its  application  to  man- 
kind. 

[  The  remainder  of  the  essay,  which  as  implied,  deals  with  the  ap- 
plication of  this  general  principle  to  the  multiplication  of  the  human 
race,  need  not  be  here  reproduced.  The  subject  is  treated  in  full  in 
Part  VI.} 


APPENDIX  B. 


THE   INADEQUACY   OF   NATURAL   SELECTION, 
ETC.,   ETC. 

[In  this  Appendix  are  included  four  essays  originally  published 
in  the  Contemporary  Review  and  subsequently  republished  as  pam- 
phlets. The  first  appeared  under  the  above  title  in  February  and 
March,  1893;  the  second  in  May  of  that  year  under  the  title 
"Prof.  Weismann's  Theories;"  the  third  in  December  of  that  year 
under  the  title  "A  Rejoinder  to  Prof.  Weismann  ;  "  and  the  fourth 
in  October,  1894,  under  the  title  "  Weismannism  Once  More."  As 
these  successive  essays  practically  form  parts  of  one  whole,  I  have 
thought  it  needless  to  keep  them  separate  by  repeating  their  titles, 
and  have  simply  marked  them  off  from  one  another  by  the  numbers 
I,  II,  III,  IV.  Of  course,  as  they  are  components  of  a  controversy, 
some  incompleteness  arises  from  the  absence  of  the  essays  to  which 
portions  of  them  were  replies  ;  but  in  each  the  course  of  the  argu- 
ment sufficiently  indicates  the  counter-arguments  which  were  metJ\ 

I. 

STUDENTS  of  psychology  are  familiar  with  the  experiments  of 
Weber  on  the  sense  of  touch.  He  found  that  different  parts 
of  the  surface  differ  widely  in  their  ability  to  give  information 
concerning  the  things  touched.  Some  parts,  which  yielded  vivid 
sensations,  yielded  little  or  no  knowledge  of  the  sizes  or  forms  of 
the  things  exciting  them ;  whereas  other  parts,  from  which  there 
came  sensations  much  less  acute,  furnished  clear  impressions 
respecting  the  tangible  characters,  even  of  relatively  small 
objects.  These  unlikenesses  of  tactual  discriminativeness  he 
ingeniously  expressed  by  actual  measurements.  Taking  a  pair 
of  compasses,  he  found  that  if  they  were  closed  so  nearly  that 
the  points  were  less  than  one-twelfth  of  an  inch  apart,  the  end  of 
the  forefinger  could  not  perceive  that  there  were  two  points :  the 
two  points  seemed  one.  But  when  the  compasses  were  opened 
so  that  the  points  were  one-twelfth  of  an  inch  apart,  then  the  end 
of  the  forefinger  distinguished  the  two  points.  At  the  same 
time,  he  found  that  the  compasses  must  be  opened  to  the  extent 
of  two  and  a  half  inches,  before  the  middle  of  the  back  could 
distinguish  between  two  points  and  one.  That  is  to  say,  as  thus 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.       003 

measured,  the  end  of  the  forefinger  has  thirty  times  the  tactual 
discriminativeness  which  the  middle  of  the  back  has. 

Between  these  extremes  he  found  gradations.  The  inner 
surfaces  of  the  second  joints  of  the  fingers  can  distinguish 
separateness  of  positions  only  half  as  well  as  the  tip  of  the 
forefinger.  The  innermost  joints  are  still  less  discriminating, 
but  have  powers  of  discrimination  equal  to  that  of  the  tip  of 
the  nose.  The  end  of  the  great  toe,  the  palm  of  the  hand,  and 
the  cheek,  have  alike  one-fifth  of  the  perceptiveness  which  the 
tip  of  the  forefinger  has  ;  and  the  lower  part  of  the  forehead  has 
but  one-half  that  possessed  by  the  cheek.  The  back  of  the  hand 
and  the  crown  of  the  head  are  nearly  alike  in  having  but  a  four- 
teenth or  a  fifteenth  of  the  ability  to  perceive  positions  as  dis- 
tinct, which  is  possessed  by  the  finger-end.  The  thigh,  near  the 
knee,  has  rather  less,  and  the  breast  less  still ;  so  that  the  com- 
passes must  be  opened  more  than  an  inch  and  a  half  before  the 
breast  distinguishes  the  two  points  from  one  another. 

What  is  the  meaning  of  these  differences  ?  How,  in  the  course 
of  evolution,  have  they  been  established  ?  If  "  natural  selec- 
tion," or  survival  of  the  fittest,  is  the  assigned  cause,  then  it  is 
required  to  show  in  what  way  each  of  these  degrees  of  endow- 
ment has  advantaged  the  possessor  to  such  extent  that  not  infre- 
quently life  has  been  directly  or  indirectly  preserved  by  it.  We 
might  reasonably  assume  that  in  the  absence  of  some  differentiat- 
ing process,  all  parts  of  the  surface  would  have  like  powers  of 
perceiving  relative  positions.  They  cannot  have  become  widely 
unlike  in  perceptiveness  without  some  cause.  And  if  the  cause 
alleged  is  natural  selection,  then  it  is  necessary  to  show  that  the 
greater  degree  of  the  power  possessed  by  this  part  than  by  that, 
has  not  only  conduced  to  the  maintenance  of  life,  but  has  con- 
duced so  much  that  an  individual  in  whom  a  variation  has  pro- 
duced better  adjustment  to  needs,  thereby  maintained  life  when 
some  others  lost  it;  and  that  among  the  descendants  inheriting 
this  variation,  there  was  a  derived  advantage  such  as  enabled 
them  to  multiply  more  than  the  descendants  of  individuals  not 
possessing  it.  Can  this,  or  anything  like  this,  be  shown  ? 

That  the  superior  perceptiveness  of  the  forefinger-tip  has  thus 
arisen,  might  be  contended  with  some  apparent  reason.  Such 
perceptiveness  is  an  important  aid  to  manipulation,  and  may 
have  sometimes  given  a  life-saving  advantage.  In  making 
arrows  or  fish-hooks,  a  savage  possessing  some  extra  amount  of  it 
may  have  been  thereby  enabled  to  get  food  where  another  failed. 
In  civilized  life,  too,  a  sempstress  with  well-endowed  finger-ends 
might  be  expected  to  gain  a  better  livelihood  than  one  with 
iinger-ends  which  were  obtuse ;  though  this  advantage  would  not 
be  so  great  as  appears.  I  have  found  that  two  ladies  whose* 


604  APPENDIX  B. 

finger-ends  were  covered  with  glove-tips,  reducing  their  sensitive- 
ness from  one-twelfth  of  an  inch  between  compass-points  to  one- 
seventh,  lost  nothing  appreciable  of  their  quickness  and  goodness 
in  sewing.  An  experience  of  my  own  here  comes  in  evidence. 
Towards  the  close  of  my  salmon-fishing  days  I  used  to  observe 
what  a  bungler  I  had  become  in  putting  on  and  taking  off  arti- 
ficial flies.  As  the  tactual  discriminativeness  of  my  finger-ends, 
recently  tested,  comes  up  to  the  standard  specified  by  Weber,  it 
is  clear  that  this  decrease  of  manipulative  power,  accompanying 
increase  of  age,  was  due  to  decrease  in  the  delicacy  of  muscular 
co-ordination  and  sense  of  pressure — not  to  decrease  of  tactual 
discriminativeness.  But  not  making  much  of  these  criticisms,  let 
us  admit  the  conclusion  that  this  high  perceptive  power  possessed 
by  the  forefinger-end  may  have  arisen  by  survival  of  the  fittest ; 
and  let  us  limit  the  argument  to  the  other  differences. 

How  about  the  back  of  the  trunk  and  its  face  ?  Is  any  advan- 
tage derived  from  possession  of  greater  tactual  discriminativeness 
by  the  last  than  the  first  ?  The  tip  of  the  nose  has  more  than 
three  times  the  power  of  distinguishing  relative  positions  which 
the  lower  part  of  the  forehead  has.  Can  this  greater  power  be 
shown  to  have  any  advantage  ?  The  back  of  the  hand  has 
scarcely  more  discriminative  ability  than  the  crown  of  the  head, 
and  has  only  one-fourteenth  of  that  which  the  finger-tip  has. 
Why  is  this  ?  Advantage  might  occasionally  be  derived  if  the 
back  of  the  hand  could  tell  us  more  than  it  does  about  the  shapes 
of  the  surfaces  touched.  WThy  should  the  thigh  near  the  knee  be 
twice  as  perceptive  as  the  middle  of  the  thigh  ?  And,  last  of  all, 
why  should  the  middle  of  the  forearm,  middle  of  the  thigh, 
middle  of  the  back  of  the  neck,  and  middle  of  the  back,  all  stand 
on  the  lowest  level,  as  having  but  one-thirtieth  of  the  perceptive 
power  which  the  tip  of  the  forefinger  has  ?  To  prove  that  these 
differences  have  arisen  by  natural  selection,  it  has  to  be  shown 
that  such  small  variation  in  one  of  the  parts  as  might  occur  in  a 
generation — say  one-tenth  extra  amount — has  yielded  an  appre- 
ciably greater  power  of  self-preservation  ;  and  that  those  inherit- 
ing it  have  continued  to  be  so  far  advantaged  as  to  multiply 
more  than  those  who,  in  other  respects  equal,  were  less  endowed 
with  this  trait.  Does  any  one  think  he  can  show  this  ? 

But  if  this  distribution  of  tactual  perceptiveness  cannot  be 
explained  by  survival  of  the  fittest,  how  can  it  be  explained  ? 
The  reply  is  that,  if  there  has  been  in  operation  a  cause  which  it 
is  now  the  fashion  among  biologists  to  ignore  or  deny,  these 
various  differences  are  at  once  accounted  for.  This  cause  is  the 
inheritance  of  acquired  characters.  As  a  preliminary  to  setting 
forth  the  argument  showing  this,  I  have  made  some  experiments. 

It  is  a  current  belief  that  the  fingers  of  the  blind,  more  prac- 


INADEQUACY   OP  NATURAL  SELECTION,   ETC.      605 

tised  in  tactual  exploration  than  the  fingers  of  those  who  can  see, 
acquire  greater  discriininativeness :  especially  the  fingers  of  those 
blind  who  have  been  taught  to  read  from  raised  letters.  Not 
wishing  to  trust  to  this  current  belief,  I  recently  tested  two 
youths,  one  of  fifteen  and  the  other  younger,  at  the  School  for 
the  Blind  in  Upper  Avenue  Road,  and  found  the  belief  to  be 
correct.  I  found  that  instead  of  being  unable  to  distinguish 
between  points  of  the  compasses  until  they  were  opened  to  one- 
twelfth  of  an  inch  apart,  both  of  them  could  distinguish  between 
points  when  only  one-fourteenth  of  an  inch  apart.  They  had 
thick  and  coarse  skins;  and  doubtless,  had  the  intervening 
obstacle,  so  produced,  been  less,  the  discriminative  power  would 
have  been  greater.  It  afterwards  occurred  to  me  that  a  better 
test  would  be  furnished  by  those  whose  finger-ends  are  exercised 
in  tactual  perceptions,  not  occasionally,  as  by  the  blind  in  read- 
ing, but  all  day  long  in  pursuit  of  their  occupations.  The  facts 
answered  expectation.  Two  skilled  compositors,  on  whom  I 
experimented,  were  both  able  to  distinguish  between  points  when 
they  were  only  one-seventeenth  of  an  inch  apart.  Thus  we  have 
clear  proof  that  constant  exercise  of  the  tactual  nervous  struc- 
ture leads  to  further  development.* 

Now  if  acquired  structural  traits  are  inheritable,  the  various 
contrasts  above  set  down  are  obvious  consequences ;  for  the 
gradations  in  tactual  perceptiveness  correspond  with  the  grada- 
tions in  the  tactual  exercises  of  the  parts.  Save  by  contact  with 
clothes,  which  present  only  broad  surfaces  having  but  slight  and 
indefinite  contrast,  the  trunk  has  scarcely  any  converse  with 

*  Let  me  here  note  in  passing  a  highly  significant  implication.  The 
development  of  nervous  structures  which  in  such  cases  take  place,  cannot 
be  limited  to  the  finger-ends.  If  we  figure  to  ourselves  the  separate  sensi- 
tive areas  which  severally  yield  independent  feelings,  as  constituting  a  net- 
work (not,  indeed,  a  network  sharply  marked  out,  but  probably  one  such  that 
the  ultimate  fibrils  in  each  area  intrude  more  or  less  into  adjacent  areas,  so 
that  the  separations  are  indefinite),  it  is  manifest  that  when,  with  exercise,  the 
structure  has  become  further  elaborated,  and  the  meshes  of  the  network 
smaller,  there  must  be  a  multiplication  of  fibres  communicating  with  the  cen- 
tral nervous  system.  If  two  adjacent  areas  were  supplied  by  branches  of  one 
fibre,  the  touching  of  either  would  yield  to  consciousness  the  same  sensation : 
there  could  be  no  discrimination  between  points  touching  the  two.  That 
there  may  be  discrimination,  there  must  be  a  distinct  connection  between  each 
area  and  the  tract  of  grey  matter  which  receives  the  impfessions.  Nay  more, 
there  must  be,  in  this  central  recipient-tract,  an  added  number  of  the  separate 
elements  which,  by  their  excitements,  yield  separate  feelings.  So  that  this  in- 
creased power  of  tactual  discrimination  implies  a  peripheral  development,  a 
multiplication  of  fibres  in  the  trunk-nerve,  and  a  complication  of  the  nerve- 
centre.  It  can  scarcely  be  doubted  that  analogous  changes  occur  under 
analogous  conditions  throughout  all  parts  of  the  nervous  system — not  in  its 
sensory  appliances  only,  but  in  all  its  higher  co-ordinating  appliances,  up  to 
the  highest. 


606  APPENDIX  I). 

external  bodies,  and  it  has  but  small  discriminative  power ;  but 
what  discriminative  power  it  has  is  greater  on  its  face  than  on 
its  back,  corresponding  to  the  fact  that  the  chest  and  abdomen 
are  much  more  frequently  explored  by  the  hands  :  this  differ- 
ence being  probably  in  part  inherited  from  inferior  creatures ;  for, 
as  we  may  see  in  dogs  and  cats,  the  belly  is  far  more  accessible 
to  feet  and  tongue  than  the  back.  No  less  obtuse  than  the  back 
are  the  middle  of  the  back  of  the  neck,  the  middle  of  the  fore- 
arm, and  the  middle  of  the  thigh ;  and  these  parts  have  but  rare 
experiences  of  irregular  foreign  bodies.  The  crown  of  the  head 
is  occasionally  felt  by  the  fingers,  as  also  the  back  of  one  hand 
by  the  fingers  of  the  other ;  but  neither  of  these  surfaces,  which 
are  only  twice  as  perceptive  as  the  back,  is  used  with  any 
frequency  for  touching  objects,  much  less  for  examining  them. 
The  lower  part  of  the  forehead,  though  more  perceptive  than  the 
crown  of  the  head,  in  correspondence  with  a  somewhat  greater 
converse  with  the  hands,  is  less  than  one-third  as  perceptive  as 
the  tip  of  the  nose ;  and  manifestly,  both  in  virtue  of  its  relative 
prominence,  in  virtue  of  its  contacts  with  things  smelt  at,  and  in 
virtue  of  its  frequent  acquaintance  with  the  handkerchief,  the  tip 
of  the  nose  has  far  greater  tactual  experience.  Passing  to  the 
inner  surfaces  of  the  hands,  which,  taken  as  wholes,  are  more 
constantly  occupied  in  touching  than  are  the  back,  breast,  thigh, 
forearm,  forehead,  or  back  of  the  hand,  Weber's  scale  shows  that 
they  are  much  more  perceptive,  and  that  the  degrees  of  percep- 
tiveness  of  different  parts  correspond  with  their  tactual  activities. 
The  palms  have  but  one-fifth  the  perceptiveness  possessed  by  the 
forefinger-ends ;  the  inner  surfaces  of  the  finger-joints  next  the 
palms  have  but  one-third;  while  the  inner  surfaces  of  the  second 
joints  have  but  one-half.  These  abilities  correspond  with  the 
facts  that  whereas  the  inner  parts  of  the  hand  are  used  only  in 
grasping  things,  the  tips  of  the  fingers  come  into  play  not  only 
when  things  are  grasped,  but  when  such  things,  as  well  as  smaller 
things,  are  felt  at  or  manipulated.  It  needs  but  to  observe  the 
relative  actions  of  these  parts  in  writing,  in  sewing,  in  judging 
textures,  &c.,  to  see  that  above  all  other  parts  the  finger-ends, 
and  especially  the  forefinger-ends,  have  the  most  multiplied  expe- 
riences. If,  then,  it  be  that  the  extra  perceptiveness  acquired 
from  actual  tactual  activities,  as  in  a  compositor,  is  inheritable, 
these  gradations  of  ta'ctual  perceptiveness  are  explained. 

Doubtless  some  of  those  who  remember  Weber's  results,  have 
had  on  the  tip  of  the  tongue  the  argument  derived  from  the  tip 
of  the  tongue.  This  part  exceeds  all  other  parts  in  power  of 
tactual  discrimination  :  doubling,  in  that  respect,  the  power  of. 
the  forefinger-tip.  It  can  distinguish  points  that  are  only  one- 
twenty-fourth  of  an  inch  apart.  Why  this  unparalleled  perceptive- 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      GO 7 

ness  ?  If  survival  of  the  fittest  be  the  ascribed  cause,  then  it  lias 
to  be  shown  what  the  advantages  achieved  have  been  ;  and,  fur- 
ther, that  those  advantages  have  been  sufficiently  great  to  have 
had  effects  on  the  maintenance  of  life. 

Besides  tasting,  there  are  two  functions  conducive  to  life,  which 
the  tongue  performs.  It  enables  us  to  move  about  food  during 
mastication,  and  it  enables  us  to  make  many  of  the  articulations 
constituting  speech.  But  how  does  the  extreme  discriminative- 
ness  of  the  tongue-tip  aid  these  functions  ?  The  food  is  moved 
about,  not  by  the  tongue-tip,  but  by  the  body  of  the  tongue ;  and 
even  were  the  tip  largely  employed  in  this  process,  it  would  still 
have  to  be  shown  that  its  ability  to  distinguish  between  points 
one-twenty-fourth  of  an  inch  apart,  is  of  service  to  that  end, 
which  cannot  be  shown.  It  may,  indeed,  be  said  that  the  tactual 
perceptiveness  of  the  tongue-tip  serves  for  detection  of  foreign 
bodies  in  the  food,  as  plum-stones  or  as  fish-bones.  But  such 
extreme  perceptiveness  is  needless  for  the  purpose.  A  perceptive- 
ness  equal  to  that  of  the  finger-ends  would  suffice.  And  further, 
even  were  such  extreme  perceptiveness  useful,  it  could  not  have 
caused  survival  of  individuals  who  possessed  it  in  slightly  higher 
degrees  than  others.  It  needs  but  to  observe  a  dog  crunching 
small  bones,  and  swallowing  with  impunity  the  sharp-angled 
pieces,  to  see  that  but  a  very  small  amount  of  mortality  would  be 
prevented. 

But  what  about  speech  ?  Well,  neither  here  can  there  be 
shown  any  advantage  derived  from  this  extreme  perceptiveness. 
For  making  the  s  and  2,  the  tongue  has  to  be  partially  applied  to 
a  portion  of  the  palate  next  the  teeth.  Not  only,  however,  must 
the  contact  be  incomplete,  but  its  place  is  indefinite — may  be 
half  an  inch  further  back.  To  make  the  sh  and  zh,  the  contact  has 
to  be  made,  not  with  the  tip,  but  with  the  upper  surface  of  the 
tongue  ;  and  must  be  an  incomplete  contact.  Though,  for  making 
the  liquids,  the  tip  of  the  tongue  and  the  sides  of  the  tongue 
are  used,  yet  the  requisite  is  not  any  exact  adjustment  of  the  tip, 
but  an  imperfect  contact  with  the  palate.  For  the  th,  the  tip  is 
used  along  with  the  edges  of  the  tongue  ;  but  no  perfect  adjust- 
ment is  required,  either  to  the  edges  of  the  teeth,  or  to  the  junc- 
tion of  the  teeth  with  the  palate,  where  the  sound  may  equally 
well  be  made.  Though  for  the  t  and  d  complete  contact  of  the 
tip  and  edges  of  the  tongue  with  the  palate  is  required,  yet  the 
place  of  contact  is  not  definite,  and  the  tip  takes  no  more  import- 
ant share  in  the  action  than  the  sides.  Any  one  who  observes 
the  movements  of  his  tongue  in  speaking,  will  find  that  there 
occur  no  cases  in  which  the  adjustments  must  have  an  exactness 
corresponding  to  the  extreme  power  of  discrimination  which  the 
tip  possesses  :  for  speech,  this  endowment  is  useless.  Even  were 


608  APPENDIX  B. 

it  useful,  it  could  not  be  shown  that  it  has  been  developed  by 
survival  of  the  fittest ;  for  though  perfect  articulation  is  an  aid, 
yet  imperfect  articulation  has  rarely  such  an  effect  as  to  impede 
a  man  in  the  maintenance  of  his  life.  If  he  is  a  good  workman, 
a  German's  interchanges  of  Us  and  p*s  do  not  disadvantage  him. 
A  Frenchman  who,  in  place  of  the  sound  of  th,  always  makes  the 
sound  of  z,  succeeds  as  a  teacher  of  music  or  dancing,  no  less 
than  if  he  achieved  the  English  pronunciation.  Nay,  even  such 
an  imperfection  of  speech  as  that  which  arises  from  cleft  palate, 
does  not  prevent  a  man  from  getting  on  if  he  is  capable.  True, 
it  may  go  against  him  as  a  candidate  for  Parliament,  or  as  an 
"  orator  "  of  the  unemployed  (mostly  not  worth  employing).  But 
in  the  struggle  for  life  he  is  not  hindered  by  the  effect  to  the 
extent  of  being  less  able  than  others  to  maintain  himself  and 
his  offspring.  Clearly,  then,  even  if  this  unparalleled  perceptive- 
ness  of  the  tongue-tip  is  required  for  perfect  speech,  such  use  iy 
not  sufficiently  important  to  have  been  developed  by  natural 
selection. 

How,  then,  is  this  remarkable  trait  of  the  tongue-tip  to  be 
accounted  for  ?  Without  difficulty,  if  there  is  inheritance  cf 
acquired  characters.  For  the  tongue-tip  has,  above  all  other 
parts  of  the  body,  unceasing  experiences  of  small  irregularities  of 
surface.  It  is  in  contact  with  the  teeth,  and  either  consciously  or 
unconsciously  is  continually  exploring  them.  There  is  hardly  a 
moment  in  which  impressions  of  adjacent  but  different  positions 
are  not  being  yielded  to  it  by  either  the  surfaces  of  the  teeth  or 
their  edges  ;  and  it  is  continually  being  moved  about  from  some 
of  them  to  others.  No  advantage  is  gained.  It  is  simply  that 
the  tongue's  position  renders  perpetual  exploration  almost  inevit- 
able ;  and  by  perpetual  exploration  is  developed  this  unique  power 
of  discrimination.  Thus  the  law  holds  throughout,  from  this 
highest  degree  of  perceptiveness  of  the  tongue-tip  to  its  lowest 
degree  on  the  back  of  the  trunk  ;  and  no  other  explanation  of 
the  facts  seems  possible. 

"  Yes,  there  is  another  explanation,"  I  hear  some  one  say  : 
"  they  may  be  explained  by  panmixia."  Well,  in  the  first  place, 
as  the  explanation  by  panmixia  implies  that  these  gradations  of 
perceptiveness  have  been  arrived  at  by  the  dwindling  of  nervous 
structures,  there  lies  at  the  basis  of  the  explanation  an  unproved 
and  improbable  assumption  ;  and,  in  the  second  place,  even  were 
there  no  such  difficulty,  it  may  with  certainty  be  denied  that 
panmixia  can  furnish  an  explanation.  Let  us  look  at  its  preten- 
sions. 

It  was  not  without  good  reason  that  Bentham  protested 
against  metaphors.  Figures  of  speech  in  general,  valuable  as  they 


INADEQUACY  OP  NATURAL  SELECTION,   ETC.       609 

are  in  poetry  and  rhetoric,  cannot  be  used  without  danger  in  science 
and  philosophy.  The  title  of  Mr.  Darwin's  great  work  furnishes 
us  with  an  instance  of  the  misleading  effects  produced  by  them. 
It  runs : — The  Origin  of  Species  by  means  of  Natural  Selection,  or  the 
Preservation  of  favoured  Races  in  the  Struggle  for  Life.  Here  are 
two  figures  of  speech  which  conspire  to  produce  an  impression 
more  or  less  erroneous.  The  expression  "  natural  selection  "  was 
chosen  as  serving  to  indicate  some  parallelism  with  artificial 
selection — the  selection  exercised  by  breeders.  Now  selection 
connotes  volition,  and  thus  gives  to  the  thoughts  of  readers  a 
wrong  bias.  Some  increase  of  this  bias  is  produced  by  the  words  in 
the  second  title,  "  favoured  races ;  "  for  anything  which  is  favoured 
implies  the  existence  of  some  agent  conferring  a  favour.  I  do 
not  mean  that  Mr.  Darwin  himself  failed  to  recognize  the  mis- 
leading connotations  of  his  words,  or  that  he  did  not  avoid  being 
misled  by  them.  In  chapter  iv  of  the  Origin  of  Species,  he  says 
that,  considered  literally,  "  natural  selection  is  a  false  term,"  and 
that  the  personification  of  Nature  is  objectionable  ;  but  he  thinks 
that  readers,  and  those  who  adopt  his  views,  will  soon  learn  to 
guard  themselves  against  the  wrong  implications.  Here  I  venture 
to  think  that  he  was  mistaken.  For  thinking  this,  there  is  the 
reason  that  even  his  disciple,  Mr.  Wallace — no,  not  his  disciple, 
but  his  co-discoverer,  ever  to  be  honoured — has  apparently  been 
influenced  by  them.  When,  for  example,  in  combating  a  view 
of  mine,  he  says  that  "  the  very  thing  said  to  be  impossible  by 
variation  and  natural  selection  has  been  again  and  again  effected 
by  variation  and  artificial  selection,"  he  seems  clearly  to  imply 
that  the  processes  are  analogous,  and  operate  in  the  same  way. 
Now  this  is  untrue.  They  are  analogous  only  within  certain 
narrow  limits  ;  and,  in  the  great  majority  of  cases,  natural  selec- 
tion is  utterly  incapable  of  doing  that  which  artificial  selection 
does. 

To  see  this  it  needs  only  to  de-personalise  Nature,  and  to  re- 
member that,  as  Mr.  Darwin  says,  Nature  is  "  only  the  aggregate 
action  and  product  of  many  natural  laws  [forces]."  Observe  its 
relative  shortcomings.  Artificial  selection  can  pick  out  a  par- 
ticular trait,  and,  regardless  of  other  traits  of  the  individuals 
displaying  it,  can  increase  it  by  selective  breeding  in  successive 
generations.  For,  to  the  breeder  or  fancier,  it  matters  little 
whether  such  individuals  are  otherwise  well  constituted.  They 
may  be  in  this  or  that  way  so  unfit  for  carrying  on  the  struggle 
for  life,  that  were  they  without  human  care,  they  would  disappear 
forthwith.  On  the  other  hand,  if  we  regard  Nature  as  that 
which  it  is,  an  assemblage  of  various  forces,  inorganic  and  organic, 
some  favourable  to  the  maintenance  of  life  and  many  at  variance 
with  its  maintenance — forces  which  operate  blindly — we  see  that 


610  APPENDIX  B. 

there  is  no  such  selection  of  this  or  that  trait ;  but  that  there  is 
a  selection  only  of  individuals  which  are,  by  the  aggregate  of 
their  traits,  best  fitted  for  living.  And  here  I  may  note  an 
advantage  possessed  by  the  expression  "  survival  of  the  fittest ; " 
since  this  does  not  tend  to  raise  the  thought  of  any  one  character 
which,  more  than  others,  is  to  be  maintained  or  increased ;  but 
tends  rather  to  raise  the  thought  of  a  general  adaptation  for  all 
purposes.  It  implies  the  process  which  Nature  can  alone  carry 
on — the  leaving  alive  of  those  which  are  best  able  to  utilize  sur- 
rounding aids  to  life,  and  best  able  to  combat  or  avoid  surround- 
ing dangers.  And  while  this  phrase  covers  the  great  mass  of 
cases  in  which  there  are  preserved  well-constituted  individuals,  it 
also  covers  those  special  cases  which  are  suggested  by  the  phrase 
"  natural  selection,"  in  which  individuals  succeed  beyond  others 
in  the  struggle  for  life,  by  the  help  of  particular  characters  which 
conduce  in  important  ways  to  prosperity  and  multiplication.  For 
now  observe  the  fact  which  here  chiefly  concerns  us,  that  survival 
of  the  fittest  can  increase  any  serviceable  trait,  only  if  that  trait 
conduces  to  prosperity  of  the  individual,  or  of  posterity,  or  of 
both,  in  an  important  degree.  There  can  be  no  increase  of  any 
structure  by  natural  selection  unless,  amid  all  the  slightly  vary- 
ing structures  constituting  the  organism,  increase  of  this  particu- 
lar one  is  so  advantageous  as  to  cause  greater  multiplication  of 
the  family  in  which  it  arises  than  of  other  families.  Variations 
which,  though  advantageous,  fail  to  do  this,  must  disappear  again. 
Let  us  take  a  case. 

Keenness  of*scent  in  a  deer,  by  giving  early  notice  of  approach- 
ing enemies,  subserves  life  so  greatly  that,  other  things  equal,  an 
individual  having  it  in  an  unusual  degree  is  more  likely  than 
others  to  survive  ;  and,  among  descendants,  to  leave  some  simi- 
larly endowed  or  more  endowed,  who  again  transmit  the-  variation 
with,  in  some  cases,  increase.  Clearly  this  highly  useful  power 
may  be  developed  by  natural  selection.  So  also,  for  like  reasons, 
may  quickness  of  vision  and  delicacy  of  hearing ;  though  it  may 
be  remarked  in  passing  that  since  this  extra  sense-endowment, 
serving  to  give  early  alarm,  profits  the  herd  as  a  whole,  which 
takes  the  alarm  from  one  individual,  selection  of  it  is  not  so  easy, 
unless  it  occurs  in  a  conquering  stag.  But  now  suppose  that  one 
member  of  the  herd — perhaps  because  of  more  efficient  teeth, 
perhaps  by  greater  muscularity  of  stomach,  perhaps  by  secretion 
of  more  appropriate  gastric  juices — is  enabled  to  eat  and  digest  a 
not  uncommon  plant  which  the  others  refuse.  This  peculiarity 
may,  if  food  is  scarce,  conduce  to  better  self -maintenance,  and 
better  fostering  of  young  if  the  individual  is  a  hind.  But  unless 
this  plant  is  abundant,  and  the  advantage  consequently  great, 
the  advantages  which  other  members  of  the  herd  gain  from  other 


INADEQUACY  OP  NATURAL  SELECTION,   ETC.       611 

slight  variations  may  be  equivalent.  This  one  has  unusual 
agility,  and  leaps  a  chasm  which  others  balk  at.  That  one  de- 
velops longer  hair  in  winter,  and  resists  the  cold  better.  Another 
has  a  skin  less  irritated  by  flies,  and  can  graze  without  so  much 
interruption.  Here  is  one  which  has  an  unusual  power  of  detect- 
ing food  under  the  snow ;  and  there  is  one  which  shows  extra 
sagacity  in  the  choice  of  a  shelter  from  wind  and  rain.  That  the 
variation  giving  ability  to  eat  a  plant  before  unutilized,  may 
become  a  trait  of  the  herd,  and  eventually  of  a  variety,  it  is  need- 
ful that  the  individual  in  which  it  occurs  shall  have  more  de- 
scendants, or  better  descendants,  or  both,  than  have  the  various 
other  individuals  severally  having  their  small  superiorities.  If 
these  other  individuals  severally  profit  by  their  small  superiori- 
ties, and  transmit  them  to  equally  large  numbers  of  offspring,  no 
increase  of  the  variation  in  question  can  take  place :  it  must  soon 
be  cancelled.  Whether  in  the  Origin  of  Species  Mr.  Darwin  has 
recognized  this  fact,  I  do  not  remember,  but  he  has  certainly 
done  it  by  implication  in  his  Animals  and  Plants  under  Domestica- 
tion. Speaking  of  variations  in  domestic  animals,  he  there  says 
that  "  any  particular  variation  would  generally  be  lost  by  crossing, 
reversion,  and  the  accidental  destruction  of  the  varying  individu- 
als, unless  carefully  preserved  by  man."  (Vol.  II,  p.  292.)  That 
which  survival  of  the  fittest  does  in  cases  like  the  one  I  have 
instanced,  is  to  keep  all  faculties  up  to  the  mark,  by  destroying 
such  individuals  as  have  faculties  in  some  respect  below  the  mark ; 
and  it  can  produce  development  of  some  one  faculty  only  if  that 
faculty  is  predominantly  important.  It  seems  to  me  that  many 
naturalists  have  practically  lost  sight  of  this,  and  assume  that 
natural  selection  will  increase  any  advantageous  trait.  Certainly 
a  view  now  held  by  some  assumes  as  much. 

The  consideration  of  this  view,  to  which  the  foregoing  para- 
graph is  introductory,  may  now  be  entered  upon.  This  view  con- 
cerns, not  direct  selection,  but  what  has  been  called,  in  question- 
able logic,  "  reversed  selection  " — the  selection  which  effects,  not 
increase  of  an  organ,  but  decrease  of  it.  For  as,  under  some  con- 
ditions, it  is  of  advantage  to  an  individual  and  its  descendants  to 
have  some  structure  of  larger  size,  it  may  be,  under  other  condi- 
tions— namely,  when  the  organ  becomes  useless — of  advantage  to 
have  it  of  smaller  size ;  since,  even  if  it  is  not  in  the  way,  its 
weight  and  the  cost  of  its  nutrition  are  injurious  taxes  on  the 
organism.  But  now  comes  the  truth  to  be  emphasized.  Just  as 
direct  selection  can  increase  an  organ  only  in  certain  cases,  so  can 
reversed  selection  decrease  it  only  in  certain  cases.  Like  the 
increase  produced  by  a  variation,  the  decrease  produced  by  one 
must  be  such  as  will  sensibly  conduce  to  preservation  and  multi- 
plication. It  is,  for  instance,  conceivable  that  were  the  long  and 


(512  APPENDIX  B. 

massive  tail  of  the  kangaroo  to  become  useless  (say  by  the  forcing 
of  the  species  into  a  mountainous  and  rocky  habitat  filled  with 
brushwood),  a  variation  which  considerably  reduced  the  tail 
might  sensibly  profit  the  individual  in  which  it  occurred ;  and,  in 
seasons  when  food  was  scarce,  might  cause  survival  when  indi- 
viduals with  large  tails  died.  But  the  economy  of  nutrition  must 
be  considerable  before  any  such  result  could  occur.  Suppose 
that  in  this  new  habitat  the  kangaroo  had  no  enemies ;  and  sup- 
pose that,  consequently,  quickness  of  hearing  not  being  called 
for,  large  ears  gave  no  greater  advantage  than  small  ones.  Would 
an  individual  with  smaller  ears  than  usual,  survive  and  propagate 
better  than  other  individuals,  in  consequence  of  the  economy  of 
nutrition  achieved  ?  To  suppose  this  is  to  suppose  that  the  sav- 
ing of  a  grain  or  two  of  protein  per  day  would  determine  the 
kangaroo's  fate. 

Long  ago  I  discussed  this  matter  in  the  Principles  of  Biology 
(§  166),  taking  as  an  instance  the  decrease  of  the  jaw  implied  by 
the  crowding  of  the  teeth,  and  now  proved  by  measurement  to 
have  taken  place.  Here  is  the  passage : — 

"  No  functional  superiority  possessed  by  a  small  jaw  over  a  large  jaw,  in 
civilized  life,  can  be  named  as  having  caused  the  more  frequent  survival  of 
small-jawed  individuals.  The  only  advantage  which  smallness  of  jaw  might 
be  supposed  to  give,  is  the  advantage  of  economized  nutrition  ;  and  this 
could  not  be  great  enough  to  further  the  preservation  of  men  possessing  it. 
The  decrease  of  weight  in  the  jaw  and  co  operative  parts  that  has  arisen  in 
the  course  of  many  thousands  of  years,  does  not  amount  to  more  than  a  few 
ounces.  This  decrease  has  to  be  divided  among  the  many  generations  that 
have  lived  and  died  in  the  interval.  Let  us  admit  that  the  weight  of  these 
parts  diminished  to  the  extent  of  an  ounce  in  a  single  generation  (which  is  a 
large  admission) ;  it  still  cannot  be  contended  that  the  having  to  carry  an 
ounce  less  in  weight,  or  having  to  keep  in  repair  an  ounce  less  of  tissue,  could 
sensibly  affect  any  man's  fate.  And  if  it  never  did  this — nay,  if  it  did  not 
cause  a  frequent  survival  of  small-jawed  individuals  where  large-jawed  indi- 
viduals died,  natural  selection  could  neither  cause  nor  aid  diminution  of  the 
jaw  and  its  appendages." 

When  writing  this  passage  in  1864,  I  never  dreamt  that  a 
quarter  of  a  century  later,  the  supposable  cause  of  degeneration 
here  examined  and  excluded  as  impossible,  would  be  enunciated 
as  an  actual  cause  and  named  "  reversed  selection." 

One  of  the  arguments  used  to  show  the  adequacy  of  natural 
selection  under  its  direct  or  indirect  form  consists  of  a  counter- 
argument to  the  effect  that  inheritance  of  functionally-wrought 
changes,  supposing  it  to  be  operative,  does  not  explain  certain  of 
the  facts.  This  is  alleged  by  Prof.  Weismann  as  a  part  justification 
for  his  doctrine  of  Panmixia.  Concerning  the  "  blind  fish  and 
amphibia  "  found  in  dark  places,  which  have  but  rudimentary  eyes 
"  1'idden  under  the  skin,"  he  argues  that  "  it  is  difficult  to  reconcile 
the  facts  of  the  case  with  the  ordinary  theory  that  the  eyes  of  these 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      613 

animals  have  simply  degenerated  through  disuse."  After  giving 
instances  of  rapid  degeneration  of  disused  organs,  he  argues  that 
if  "  the  effects  of  disuse  are  so  striking  in  a  single  life,  we  should 
certainly  expect,  if  such  effects  can  be  transmitted,  that  all  traces 
of  an  eye  would  soon  disappear  from  a  species  which  lives  in  the 
dark."  Doubtless  this  is  a  reasonable  conclusion.  To  explain 
the  facts  on  the  hypothesis  that  acquired  characters  are  inheri- 
table, seems  very  difficult.  One  possible  explanation  may,  in- 
deed, be  named.  It  appears  to  be  a  general  law  of  organization 
that  structures  are  stable  in  proportion  to  their  antiquity — that 
while  organs  of  relatively  modern  origin  have  but  a  comparatively 
superficial  root  in  the  constitution,  and  readily  disappear  if  the 
conditions  do  not  favour  their  maintenance,  organs  of  ancient 
origin  have  deep-seated  roots  in  the  constitution,  and  do  not 
readily  disappear.  Having  been  early  elements  in  the  type,  and 
having  continued  to  be  reproduced  as  parts  of  it  during  a  period 
extending  throughout  many  geological  epochs,  they  are  compara- 
tively persistent.  Now  the  eye  answers  to  this  description  as 
being  a  very  early  organ.  But  waiving  possible  explanations, 
let  us  take  the  particular  instance  cited  by  Prof.  Weismann  and 
see  what  is  to  be  made  of  it.  He  writes  : — 

"  The  caverns  in  Carniola  and  Carinthia,  in  which  the  blind  Proteus  and 
so  many  other  blind  animals  live,  belong  geologically  to  the  Jurassic 
formation ;  and  although  we  do  not  exactly  know  when  for  example  the 
Proteus  first  entered  them,  the  low  organization  of  this  amphibian  certainly 
indicates  that  it  has  been  sheltered  there  for  a  very  long  period  of  time,  and 
that  thousands  of  generations  of  this  species  have  succeeded  one  another  in 
the  caves. 

"  Hence  there  is  no  reason  to  wonder  at  the  extent  to  which  the  degene- 
ration of  the  eye  has  been  already  carried  in  the  Proteus  ;  even  if  we  assume 
that  it  is  merely  due  to  the  cessation  of  the  conserving  influence  of  natural 
selection."  * 

Let  me  first  note  a  strange  oversight  on  the  part  of  Prof. 
Weismann.  He  points  out  that  the  caverns  in  question  belong 
to  the  Jurassic  formation  :  apparently  intending  to  imply  that 
they  have  an  antiquity  related  to  that  of  the  formation.  But 
there  is  no  such  relation,  except  that  the  caverns  cannot  be  older 
than  the  formation.  They  may  have  originated  at  any  period 
since  the  containing  strata  were  deposited  ;  and  they  may  be 
therefore  relatively  modern.  But  passing  over  this,  and  admit- 
ting that  the  Proteus  has  inhabited  the  caverns  for  an  enormous 
period,  what  is  to  be  said  of  the  fact  that  their  eyes  have  not 
disappeared  entirely,  as  Prof.  Weismann  contends  they  should 
have  done  had  the  inheritance  of  the  effects  of  disuse  been  all 
along  operative  ?  There  is  a  very  sufficient  answer — the  rudi- 
mentary eyes  are  not  entirely  useless.  It  seems  that  when  the 
*  Essays  upon  Heredity,  p.  87. 


614  APPENDIX  B. 

underground  streams  it  inhabits  are  unusually  swollen,  some  in- 
dividuals of  the  species  are  carried  out  of  the  caverns  into  the 
open  (being  then  sometimes  captured).  It  is  also  said  that  the 
creatures  shun  tie  light ;  this  trait  being,  I  presume,  observed 
when  it  is  in  captivity.  Now  obviously,  among  individuals 
carried  out  into  the  open,  those  which  remain  visible  are  apt  to 
be  carried  off  by  enemies  ;  whereas,  those  which,  appreciating  the 
difference  between  light  and  darkness,  shelter  themselves  in  dark 
places,  survive.  Hence  the  tendency  of  natural  selection  is  to 
prevent  th<*  decrease  of  the  eyes  beyond  that  point  at  which  they 
can  distinguish  between  light  and  darkness.  Thus  the  apparent 
anomaly  is  explained. 

Let  me  suggest,  as  another  possible  reason  for  persistence  of 
rudimentary  organs,  that  the  principle  of  economy  of  growth  will 
cause  diminution  of  them  only  in  proportion  as  their  constituents 
are  of  value  for  other  uses  in  the  organism  ;  and  that  in  many 
cases  their  constituents  are  practically  valueless.  Hence  prob- 
ably the  reason  why,  in  the  case  of  stalk-eyed  crustaceans,  the 
eye  is  gone  but  the  pedicle  remains,  or  to  use  Mr.  Darwin's  simile, 
the  telescope  has  disappeared  but  not  its  stand. 

Along  with  that  inadequacy  of  natural  selection  to  explain 
changes  of  structure  which  do  not  aid  life  in  important  ways, 
alleged  in  §  166  of  The  Principles  of  Biology,  a  further  inadequacy 
was  alleged.  It  was  contended  that  the  relative  powers  of  co- 
operative parts  cannot  be  adjusted  solely  by  survival  of  the 
fittest ;  and  especially  where  the  parts  are  numerous  and  the  co- 
operation complex.  In  illustration  it  was  pointed  out  that  im- 
mensely developed  horns,  such  as  those  of  the  extinct  Irish  elk, 
weighing  over  a  hundred-weight,  could  not,  with  the  massive 
skull  bearing  them,  be  carried  at  the  extremity  of  the  out- 
stretched neck  without  many  and  great  modifications  of  adjacent 
bones  and  muscles  of  the  neck  and  thorax  ;  and  that  without 
strengthening  of  the  fore-legs,  too,  there  would  be  failure  alike 
in  fighting  and  in  locomotion.  And  it  was  argued  that  while  we 
cannot  assume  spontaneous  increase  of  all  these  parts  propor- 
tionate to  the  additional  strains,  we  cannot  suppose  them  to  in- 
crease by  variations,  one  at  once,  without  supposing  the  creature 
to  be  disadvantaged  by  the  weight  and  nutrition  of  parts  that 
were  for  the  time  useless — parts,  moreover,  which  would  revert 
to  their  original  sizes  before  the  other  needful  variations  occurred. 

When,  in  reply  to  me,  it  was  contended  that  co-operative  parts 
vary  together,  I  named  facts  conflicting  with  this  assertion — the 
fact  that  the  blind  cray-fish  of  the_  Kentucky  caves  have  lost 
their  eyes  but  not  the  foot  stalks  carrying  them  ;  the  fact  that 
the  normal  proportion  between  tongue  and  beak  in  certain 


INADEQUACY  OP  NATURAL  SELECTION,   ETC.       G15 

selected  varieties  of  pigeons  is  lost ;  the  fact  that  lack  of  con- 
comitance in  decrease  of  jaws  and  teeth  in  sundry  kinds  of  pet 
dogs,  has  caused  great  crowding  of  the  teeth  ("  The  Factors  of 
Organic  Evolution,  Essays,  i,  401-402).  And  I  then  argued  that 
if  co-operative  parts,  small  in  number  and  so  closely  associated  as 
these  are,  do  not  vary  together,  it  is  unwarrantable  to  allege  that 
co-operative  parts  which  are  very  numerous  and  remote  from  one 
another  vary  together.  After  making  this  rejoinder  I  enforced 
my  argument  by  a  further  example — that  of  the  giraffe.  Tacitly 
recognizing  the  truth  that  the  unusual  structure  of  this  creature 
must  have  been,  in  its  most  conspicuous  traits,  the  result  of  sur- 
vival of  the  fittest  (since  it  is  absurd  to  suppose  that  efforts  to 
reach  high  branches  could  lengthen  the  legs),  I  illustrated  afresh 
the  obstacles  to  co-adaptation.  Not  dwelling  on  the  objection 
that  increase  of  any  components  of  the  fore-quarters  out  of 
adjustment  to  the  others,  would  cause  evil  rather  than  good,  I 
went  on  to  argue  that  the  co-adaptation  of  parts  required  to 
make  the  giraffe's  structure  useful,  is  much  greater  than  at  first 
appears.  This  animal  has  a  grotesque  gallop,  necessitated  by  the 
great  difference  in  length  between  the  fore  and  the  hind  limbs. 
I  pointed  out  that  the  mode  of  action  of  the  hind  limbs  shows 
that  the  bones  and  muscles  have  all  been  changed  in  their  propor- 
tions and  adjustments  ;  and  I  contended  that,  difficult  as  it  is  to 
believe  that  all  parts  of  the  fore -quarters  have  been  co-adapted 
by  the  appropriate  variations,  now  of  this  part  now  of  that,  it 
becomes  impossible  to  believe  that  all  the  parts  in  the  hind- 
quarters have  been  simultaneously  co-adapted  to  one  another  and 
to  all  the  parts  of  the  fore-quarters :  adding  that  want  of  co- 
adaptation,  even  in  a  single  muscle,  would  cause  fatal  results 
when  high  speed  had  to  be  maintained  while  escaping  from  an 
enemy. 

Since  this  argument,  repeated  with  this  fresh  illustration,  was 
published  in  1886,  I  have  met  with  nothing  to  be  called  a  reply ; 
and  might,  I  think,  if  convictions  usually  followed  proofs,  leave 
the  matter  as  it  stands.  It  is  true  that,  in  his  Darwinism,  Mr. 
Wallace  has  adverted  to  my  renewed  objection,  and,  as  already 
said,  contended  that  changes  such  as  those  instanced  can  be  ef- 
fected by  natural  selection,  since  such  changes  can  be  effected  by 
artificial  selection  :  a  contention  which,  as  I  have  pointed  out, 
assumes  a  parallelism  that  does  not  exist.  But  now,  instead  of 
pursuing  the  argument  further  along  the  same  line,  let  me  take 
a  somewhat  different  line. 

If  there  occurs  some  change  in  an  organ,  say  by  increase  of  its 
size,  which  adapts  it  better  to  the  creature's  needs,  it  is  admitted 
that  when,  as  commonly  happens,  the  use  of  the  organ  demands 
the  co-operation  of  other  organs,  the  change  in  it  will  generally 


016  APPENDIX  B. 

be  of  no  service  unless  the  co-operative  organs  are  changed.  If, 
for  instance,  there  takes  place  such  a  modification  of  a  rodent's 
tail  as  that  which,  by  successive  increases,  produces  the  trowel- 
shaped  tail  of  the  beaver,  no  advantage  will  be  derived  unless 
there  also  take  place  certain  modifications  in  the  bulks  and  shapes 
of  the  adjacent  vertebrae  and  their  attached  muscles,  as  well  as, 
probably,  in  the  hind  limbs  ;  enabling  them  to  withstand  the 
reactions  of  the  blows  given  by  the  tail.  And  the  question  is, 
by  what  process  these  many  parts,  changed  in  different  degrees, 
are  co-adapted  to  the  new  requirements — whether  variation  and 
natural  selection  alone  can  effect  the  readjustment.  There  are 
threa  conceivable  ways  in  which  the  parts  may  simultaneously 
change  : — (1)  they  may  all  increase  or  decrease  together  in  like 
degree  ;  (2)  they  may  all  simultaneously  increase  or  decrease  in- 
dependently, so  as  not  to  maintain  their  previous  proportions,  or 
assume  any  other  special  proportions  ;  (3)  they  may  vary  in  such 
ways  and  degrees  as  to  make  them  jointly  serviceable  for  the  new 
end.  Let  us  consider  closely  these  several  conceivabilities. 

And  first  of  all,  what  are  we  to  understand  by  co-operative 
parts  ?  In  a  general  sense,  all  the  organs  of  the  body  are  co- 
operative parts,  and  are  respectively  liable  to  be  more  or  less 
changed  by  change  in  any  one.  In  a  narrower  sense,  more 
directly  relevant  to  the  argument,  we  may,  if  we  choose  to 
multiply  difficulties,  take  the  entire  framework  of  bones  and 
muscles  as  formed  of  co-operative  parts  ;  for  these  are  so  related 
that  any  considerable  change  in  the  actions  of  some  entails 
change  in  the  actions  of  most  others.  It  needs  only  to  observe 
how,  when  putting  out  an  effort,  there  goes,  along  with  a  deep 
breath,  an  expansion  of  the  chest  and  a  bracing  up  of  the  abdo- 
men, to  see  that  various  muscles  beyond  those  directly  concerned 
are  strained  along  with  them.  Or,  when  suffering  from  lumbago, 
an  effort  to  lift  a  chair  will  cause  an  acute  consciousness  that  not 
the  arms  only  are  brought  into  action,  but  also  the  muscles  of  the 
back.  These  cases  show  how  the  motor  organs  are  so  tied  to- 
gether that  altered  actions  of  some  implicate  others  quite  remote 
from  them. 

But  without  using  the  advantage  which  this  interpretation  of 
the  words  would  give,  let  us  take,  as  co-operative  organs,  those 
which  are  obviously  such — the  organs  of  locomotion.  What, 
then,  shall  we  say  of  the  fore  limbs  and  hind  limbs  of  terrestrial 
mammals,  which  co-operate  closely  and  perpetually  ?  Do  they 
vary  together  ?  If  so,  how  have  there  been  produced  such  con- 
trasted structures  as  that  of  the  kangaroo,  with  its  large  hind 
limbs  and  small  fore  limbs,  and  that  of  the  giraffe,  in  which  the 
hind  limbs  are  small  and  the  fore  limbs  large — how  does  it 
happen  that,  descending  from  the  same  primitive  mammal,  these 


INADEQUACY  OF  NATURAL  SELECTION,    ETC.       617 

creatures  have  diverged  in  the  proportions  of  their  limbs  in 
opposite  directions  ?  Take,  again,  the  articulate  animals.  Com- 
pare one  of  the  lower  types,  with  its  rows  of  almost  equal-sized 
limbs,  and  one  of  the  higher  types,  as  a  crab  or  a  lobster,  with 
(imbs  some  very  small  and  some  very  large.  How  came  this 
contrast  to  arise  in  the  course  of  evolution,  if  there  was  the  equality 
of  variation  supposed  ? 

But  now  let  us  narrow  the  meaning  of  the  phrase  still  further, 
giving  it  a  more  favourable  interpretation.  Instead  of  con- 
sidering separate  limbs  as  co-operative,  let  us  consider  the  com- 
ponent parts  of  the  same  limb  as  co-operative,  and  ask  what 
would  result  from  varying  together.  It  would  in  that  case 
happen  that,  though  the  fore  and  hind  limbs  of  a  mammal  might 
become  different  in  their  sizes,  they  would  not  become  different 
in  their  structures.  If  so,  how  have  there  arisen  the  unlikenesscs 
between  the  hind  legs  of  the  kangaroo  and  those  of  the  elephant  ? 
Or  if  this  comparison  is  objected  to,  because  the  creatures  belong 
to  the  widely  different  divisions  of  implacental  and  placental 
mammals,  take  the  cases  of  the  rabbit  and  the  elephant,  both 
belonging  to  the  last  division.  On  the  hypothesis  of  evolution 
these  are  both  derived  from  the  same  original  form ;  but  the  pro- 
portions of  the  parts  have  become  so  widely  unlike  that  the 
corresponding  joints  are  scarcely  recognized  as  such  by  the  un- 
observant :  at  what  seem  corresponding  places  the  legs  bend  in 
opposite  ways.  Equally  marked,  or  more  marked,  is  the  parallel 
fact  among  the  Articuluta.  Take  that  limb  of  the  lobster  which 
bears  the  claw  and  compare  it  with  the  corresponding  limb  in  an 
inferior  articulate  animal,  or  the  corresponding  limb  of  its  near 
ally,  the  rock  lobster,  and  it  becomes  obvious  that  the  component 
segments  of  the  limb  have  come  to  bear  to  one  another  in  the 
one  case,  proportions  immensely  different  from  those  they  bear 
in  the  other  case.  Undeniably,  then,  on  contemplating  the 
general  facts  of  organic  structure,  we  see  that  the  concomitant 
variations  in  the  parts  of  limbs,  have  not  been  of  a  kind  to  pro- 
duce equal  amounts  of  change  in  them,  but  quite  the  opposite 
— have  been  everywhere  producing  inequalities.  Moreover,  we 
are  reminded  that  this  production  of  inequalities  among  co-opera- 
tive parts,  is  an  essential  principle  of  development.  Had  it  not 
been  so,  there  could  not  have  been  that  progress  from  homoge- 
neity of  structure  to  heterogeneity  of  structure  which  constitutes 
evolution. 

We  pass  now  to  the  second  supposition : — that  the  variations 
in  co-operative  parts  occur  irregularly,  or  in  such  independent 
ways  that  they  bear  no  definite  relations  to  one  another — miscel- 
laneously, let  us  say.  This  is  the  supposition  which  best  corre- 
sponds with  the  facts.  Glances  at  the  faces  around  yield 


618  APPENDIX  B. 

conspicuous  proofs.  Many  of  the  muscles  of  the  face  and  some 
of  the  bones,  are  distinctly  co-operative ;  and  these  respectively 
vary  in  such  ways  as  to  produce  in  each  person  a  different  com- 
bination. What  we  see  in  the  face  we  have  reason  to  believe 
holds  in  the  limbs  and  in  all  other  parts.  Indeed,  it  needs  but  to 
compare  people  whose  arms  are  of  the  same  lengths,  and  observe 
how  stumpy  are  the  fingers  of  one  and  how  slender  those  of 
another ;  or  it  needs  but  to  note  the  unlikenesses  of  gait  of 
passers-by,  implying  small  unlikenesses  of  structure ;  to  be  con- 
vinced that  the  relations  among  the  variations  of  co-operative 
parts  are  anything  but  fixed.  And  now,  confining  our  attention 
to  limbs,  let  us  consider  what  must  happen  if,  by  variations 
Hiking  place  miscellaneously,  limbs  have  to  be  partially  changed 
from  fitness  for  one  function  to  fitness  for  another  function — have 
to  be  re-adapted.  That  the  reader  may  fully  comprehend  the 
argument,  he  must  here  have  patience  while  a  good  many  ana- 
tomical details  are  set  down. 

Let  us  suppose  a  species  of  quadruped  of  which  the  members 
have,  for  immense  past  periods,  been  accustomed  to  locomotion 
over  a  relatively  even  surface,  as,  for  instance,  the  "  prairie-dogs  " 
of  North  America  ;  and  let  us  suppose  that  increase  of  numbers 
has  driven  part  of  them  into  a  region  full  of  obstacles  to  easy 
locomotion — covered,  say,  by  the  decaying  stems  of  fallen  trees, 
such  as  one  sees  in  portions  of  primeval  forest.  Ability  to  leap 
must  then  become  a  useful  trait ;  and,  according  to  the  hypo- 
thesis we  are  considering,  this  ability  will  be  produced  by  the 
selection  of  favourable  variations.  What  are  the  variations 
required  ?  A  leap  is  effected  chiefly  by  the  bending  of  the  hind 
limbs  so  as  to  make  sharp  angles  at  the  joints,  and  then  suddenly 
straightening  them  ;  as  any  one  may  see  on  watching  a  cat  leap 
on  to  the  table.  The  first  required  change,  then,  is  increase  of  the 
large  extensor  muscles,  by  which  the  hind  limbs  are  straightened. 
Their  increases  must  be  duly  proportioned  ;  for  if  those  which 
straightened  one  joint  become  much  stronger  than  those  which 
straightened  the  other  joint,  the  result  must  be  collapse  of  the 
other  joint  when  the  muscles  are  contracted  together.  But  let 
us  make  a  large  admission,  and  suppose  these  muscles  to  vary 
together ;  what  further  muscular  change  is  next-  required  ?  In  a 
plantigrade  mammal  the  metatarsal  bones  chiefly  bear  the  reac- 
tion of  the  leap,  though  the  toes  may  have  a  share.  In  a  digiti- 
grade  mammal,  however,  the  toes  form  almost  exclusively  the 
fulcrum,  and  if  they  are  to  bear  the  reaction  of  a  higher  leap, 
the  flexor  muscles  which  depress  and  bend  them  must  be  pro- 
portionately enlarged  :  if  not,  the  leap  will  fail  from  want  of  a 
firm  point  (Tappui.  Tendons  as  well  as  muscles  must  be  modified  ; 
and,  among  others,  the  many  tendons  which  go  to  the  digits  and 


INADEQUACY  OP  NATURAL  SELECTION,   ETC.      619 

their  phalanges.  Stronger  muscles  and  tendons  imply  greater 
strains  on  the  joints ;  and  unless  these  are  strengthened,  one  or 
other,  dislocation  will  be  caused  by  a  more  vigorous  spring.  Not 
only  the  articulations  themselves  must  be  so  modified  as  to  bear 
greater  stress,  but  also  the  numerous  ligaments  which  hold  the 
parts  of  each  in  place.  Nor  can  the  bodies  of  the  bones  remain 
unstrengthened ;  for  if  they  have  no  more  than  the  strengths 
needed  for  previous  movements  they  will  fail  to  bear  more  violent 
movements.  Thus,  saying  nothing  of  the  required  changes  in 
the  pelvis,  as  well  as  in  the  nerves  and  blood-vessels,  there  are, 
counting  bones,  muscles,  tendons,  ligaments,  at  least  fifty  differ- 
ent parts  in  each  hind  leg  which  have  to  be  enlarged.  More- 
over they  have  to  be  enlarged  in  unlike  degrees.  The  muscles 
and  tendons  of  the  outer  toes,  for  example,  need  not  be  added  to 
so  much  as  those  of  the  median  toes.  Now,  throughout  their 
successive  stages  of  growth,  all  these  parts  have  to  be  kept  fairly 
well  balanced ;  as  any  one  may  infer  on  remembering  sundry  of 
the  accidents  he  has  known.  Among  my  own  friends  I  could 
name  one  who,  when  playing  lawn-tennis,  snapped  the  Achilles 
tendon ;  another  who,  while  swinging  his  children,  tore  some  of 
the  muscular  fibres  in  the  calf  of  his  leg ;  another  who,  in  getting 
over  a  fence,  tore  a  ligament  of  one  knee.  Such  facts,  joined 
with  every  one's  experience  of  sprains,  show  that  during  the 
extreme  exertions  to  which  limbs  are  now  and  then  subject,  there 
is  a  giving  way  of  parts  not  quite  up  to  the  required  level  of 
strength.  How,  then,  is  this  balance  to  be  maintained  ?  Suppose 
the  extensor  muscles  have  all  varied  appropriately ;  their  varia- 
tions are  useless  unless  the  other  co-operative  parts  have  also  varied 
appropriately.  Worse  than  this.  Saying  nothing  of  the  dis- 
advantage caused  by  extra  weight  and  cost  of  nutrition,  they  will 
be  causes  of  mischief — causes  of  derangement  to  the  rest  by  con- 
tracting with  undue  force.  And  then,  how  long  will  it  take  for 
the  rest  to  be  brought  into  adjustment  ?  As  Mr.  Darwin  says 
concerning  domestic  animals : — "  Any  particular  variation  would 
generally  be  lost  by  crossing,  reversion,  &c.  .  .  .  unless  care- 
fully preserved  by  man."  In  a  state  of  nature,  then,  favourable 
variations  of  these  muscles  would  disappear  again  long  before  one 
or  a  few  of  the  co-operative  parts  could  be  appropriately  varied, 
much  more  before  all  of  them  could. 

With  this  insurmountable  difficulty  goes  a  difficulty  still  more 
insurmountable — if  the  expression  may  be  allowed.  It  is  not  a 
question  of  increased  sizes  of  parts  only,  but  of  altered  shapes  of 
parts,  too.  A  glance  at  the  skeletons  of  mammals  shows  how 
unlike  are  the  forms  of  the  corresponding  bones  of  their  limbs ; 
and  shows  that  they  have  been  severally  re-moulded  in  each 
species  to  the  different  requirements  entailed  by  its  different 


G20  APPENDIX  B. 

habits.  The  change  from  the  structures  of  hind  limbs  fitted  only 
for  walking  and  trotting  to  hind  limbs  fitted  also  for  leaping, 
implies,  therefore,  that,  along  with  strengthenings  of  bones  there 
must  go  alterations  in  their  forms.  Now  the  fortuitous  altera- 
tions of  form  which  may  take  place  in  any  bone  are  countless. 
How  long,  then,  will  it  be  before  there  takes  place  that  particu- 
lar alteration  which  will  make  the  bone  fitter  for  its  new  action  ? 
And  what  is  the  probability  that  the  many  required  changes  of 
shape,  as  well  as  of  size,  in  bones  will  each  of  them  be  effected 
before  all  the  others  are  lost  again  ?  If  the  probabilities  against 
success  are  incalculable,  when  we  take  account  only  of  changes  in 
the  sizes  of  parts,  what  shall  we  say  of  their  incalculableness  when 
differences  of  form  also  are  taken  into  account  ? 

"  Surely  this  piling  up  of  difficulties  has  gone  far  enough  "  ; 
the  reader  will  be  inclined  to  say.  By  no  means.  There  is  a 
difficulty  immeasurably  transcending  those  named.  We  have  thus 
far  omitted  the  second  half  of  the  leap,  and  the  provisions  to  be 
made  for  it.  After  ascent  of  the  animal's  body  comes  descent ; 
and  the  greater  the  force  with  which  it  is  projected  up,  the 
greater  is  the  force  with  which  it  comes  down.  Hence,  if  the 
supposed  creature  has  undergone  such  changes  in  the  hind  limbs 
as  will  enable  them  to  propel  it  to  a  greater  height,  without 
having  undergone  any  changes  in  the  fore  limbs,  the  result  will 
be  that  on  its  descent  the  fore  limbs  will  give  way,  and  it  will 
come  down  on  its  nose.  The  fore  limbs,  then,  have  to  be 
changed  simultaneously  with  the  hind.  How  changed  ?  Con- 
trast the  markedly  bent  hind  limbs  of  a  cat  with  its  almost 
straight  fore  limbs,  or  contrast  the  silence  of  the  spring  on  to  the 
table  with  the  thud  which  the  fore  paws  make  as  it  jumps  off  the 
table.  See  how  unlike  the  actions  of  the  hind  and  fore  limbs 
are,  and  how  unlike  their  structures.  In  what  way,  then,  is  the 
required  co-adaptation  to  be  effected  ?  Even  were  it  a  question  of 
relative  sizes  only,  there  would  be  no  answer;  for  facts  already 
given  show  that  we  may  not  assume  simultaneous  increases  of 
size  to  take  place  in  the  hind  and  fore  limbs ;  and,  indeed,  a 
glance  at  the  various  human  races,  which  differ  considerably  in 
the  ratios  of  their  legs  to  their  arms,  shows  us  this.  But  it  is 
not  simply  a  question  of  sizes.  To  bear  the  increased  shock  of 
descent  the  fore  limbs  must  be  changed  throughout  in  their 
structures.  Like  those  in  the  hind  limbs,  the  changes  must  be 
of  many  parts  in  many  proportions ;  and  they  must  be  both  in 
sizes  and  in  shapes.  More  than  this.  The  scapular  arch  and  its 
attached  muscles  must  also  be  strengthened  and  re-moulded.  See, 
then,  the  total  requirements.  We  must  suppose  that  by  natural 
selection  of  miscellaneous  variations,  the  parts  of  the  hind  limbs 
will  be  co-adapted  to  one  another,  in  sizes,  shapes,  and  ratio:' ; 


INADEQUACY  OF  NATURAL  SELECTION,    ETC.       621 

that  those  of  the  fore  limbs  will  undergo  co-adaptation  similar  in 
their  complexity,  but  dissimilar  in  their  kinds  ;  and  that  the  two 
sets  of  co-adaptations  will  be  effected  pari  passu.  If,  as  may  be 
held,  the  probabilities  are  millions  to  one  against  the  first  set  of 
changes  being  achieved,  then  it  may  be  held  that  the  probabilities 
are  billions  to  one  against  the  second  being  simultaneously 
achieved,  in  progressive  adjustment  to  the  first. 

There  remains  only  to  notice  the  third  conceivable  mode  of 
adjustment.  It  may  be  imagined  that  though,  by  the  natural 
selection  of  miscellaneous  variations,  these  adjustments  cannot  be 
effected,  they  may  nevertheless  be  made  to  take  place  appro- 
priately. How  made  ?  To  suppose  them  so  made  is  to  suppose 
that  the  prescribed  end  is  somewhere  recognized ;  and  that  the 
changes  are  step  by  step  simultaneously  proportioned  for  achiev- 
ing it — is  to  suppose  a  designed  production  of  these  changes.  In 
such  case,  then,  we  have  to  fall  back  in  part  upon  the  primitive 
hypothesis ;  and  if  we  do  this  in  part,  we  may  as  well  do  it 
wholly — may  as  well  avowedly  return  to  the  doctrine  of  special 
creations. 

What,  then,  is  the  only  defensible  interpretation  ?  If  such 
modifications  of  structure  produced  by  modifications  of  function 
as  we  see  take  place  in  each  individual,  are  in  any  measure 
transmissible  to  descendants,  then  all  these  co- adaptations,  from 
the  simplest  up  to  the  most  complex,  are  accounted  for.  In  some 
cases  this  inheritance  of  acquired  characters  suffices  by  itself  to 
explain  the  facts  ;  and  in  other  cases  it  suffices  when  taken  in 
combination  with  the  selection  of  favourable  variations.  An 
example  of  the  first  class  is  furnished  by  the  change  just  con- 
sidered ;  and  an  example  of  the  second  class  is  furnished  by  the 
case,  before  named,  of  development  in  a  deer's  horns.  If,  by 
some  extra  massiveness  spontaneously  arising,  or  by  formation  of 
an  additional  "  point,"  an  advantage  is  gained  either  for  attack 
or  defence,  then,  if  the  increased  muscularity  and  strengthened 
structure  of  the  neck  and  thorax,  which  wielding  of  these  some- 
what heavier  horns  produces,  are  in  a  greater  or  less  degree 
inherited,  and  in  several  successive  generations  are  by  this 
process  brought  up  to  the  required  extra  strength,  it  becomes 
possible  and  advantageous  for  a  further  increase  of  the  horns  to 
take  place,  and  a  further  increase  in  the  apparatus  for  wielding 
them,  and  so  on  continuously.  By  such  processes  only,  in  which 
each  part  gains  strength  in  proportion  to  function,  can  co-opera- 
tive parts  be  kept  in  adjustment,  and  be  re-adjusted  to  meet  new 
requirements.  Close  contemplation  of  the  facts  impresses  me 
more  strongly  than  ever  with  the  two  alternatives — either  there 
has  been  inheritance  of  acquired  characters,  or  there  has  been  no 
evolution. 


622  APPENDIX  B. 

This  very  pronounced  opinion  will  be  met,  on  the  part  of  some, 
by  a  no  less  pronounced  demurrer,  which  involves  a  denial  of 
possibility.  It  has  been  of  late  asserted,  and  by  many  believed, 
that  inheritance  of  acquired  characters  cannot  occur.  Weismann, 
they  say,  has  shown  that  there  is  early  established  in  the  evolu- 
tion of  each  organism  such  a  distinctness  between  those  compo- 
nent units  which  carry  on  the  individual  life  and  those  which  are 
devoted  to  maintenance  of  the  species,  that  changes  in  the  one 
cannot  affect  the  other.  We  will  look  closely  into  his  doctrine. 

Basing  his  argument  on  the  principle  of  the  physiological 
division  of  labour,  and  assuming  that  the  primary  division  of 
labour  is  that  between  such  part  of  an  organism  as  carries  on 
individual  life  and  such  part  as  is  reserved  for  the  production  of 
other  lives,  Weismann,  starting  with  "  the  first  multicellular 
organism,"  says  that — "  Hence  the  single  group  would  come  to 
be  divided  into  two  groups  of  cells,  which  may  be  called  somatic 
and  reproductive — the  cells  of  the  body  as  opposed  to  those 
which  are  concerned  with  reproduction."  (Essays  upon  Heredity, 
i,  p.  27.) 

Though  he  admits  that  this  differentiation  "  was  not  at  first 
absolute,  and  indeed  is  not  always  so  to-day,"  yet  he  holds  that 
the  differentiation  eventually  becomes  absolute  in  the  sense  that 
the  somatic  cells,  or  those  which  compose  the  body  at  large,  come 
to  have  only  a  limited  power  of  cell-division,  instead  of  an  un- 
limited power  which  the  reproductive  cells  have ;  and  also  in 
the  sense  that  eventually  there  ceases  to  be  any  communication 
between  the  two  further  than  that  implied  by  the  supplying  of 
nutriment  to  the  reproductive  cells  by  the  somatic  cells.  The 
outcome  of  this  argument  is  that,  in  the  absence  of  communica- 
tion, changes  induced  in  the  somatic  cells,  constituting  the  indi- 
vidual, cannot  influence  the  natures  of  the  reproductive  cells,  and 
cannot  therefore  be  transmitted  to  posterity.  Such  is  the  theory. 
Now  let  us  look  at  a  few  facts — some  familiar,  some  unfamiliar. 

His  investigations  led  Pasteur  to  the  positive  conclusion  that 
the  silkworm  diseases  are  inherited.  The  transmission  from 
parent  to  offspring  resulted,  not  through  any  contamination  of 
the  surface  of  the  egg  by  the  body  of  the  parent  while  being 
deposited,  but  resulted  from  infection  of  the  egg  itself — intrusion 
of  the  parasitic  organism.  Generalized  observations  concerning 
the  disease  called  pebrine,  enabled  him  to  decide,  by  inspection  of 
the  eggs,  which  were  infected  and  which  were  not :  certain  modi- 
fications of  form  distinguishing  the  diseased  ones.  More  than 
this ;  the  infection  was  proved  by  microscopical  examination  of 
the  contents  of  the  egg ;  in  proof  of  which  he  quotes  as  follows 
from  Dr.  Carlo  Vittadini : — 

"  II  r6sulte  dc  mes  recherches  sur  Ics  graincs,  i  I'e'poquc  ou  commence  le 


INADEQUACY  OP   NATURAL  SELECTION,   ETC.      623 

developpement  du  gcnne,  que  les  corpusculcs,  une  fois  apparus  dans  1'oeuf, 
augmentent  graducllement  en  nombre,  a  mesure  que  1'embryon  se  developpe  ; 
que,  dans  les  derniers  jours  de  1'incubation,  1'oeuf  en  est  plein,  au  point  de 
faire  croire  que  la  majcure  partie  des  granules  du  jaune  se  sont  transformed 
en  corpusculcs. 

"  Une  autre  observation  importante  cst  que  1'embryon  aussi  est  souille  de 
corpuscules,  et  ;\  un  degre  tel  qu'on  peut  soupconner  que  1'infection  du  jaune 
tire  son  origine  du  germe  lui-meme  ;  en  d'autres  termes  que  le  germe  est  pi  i- 
mordialement  infecte,  et  porte  en  lui-meme  ces  corpuscules  tout  comme  les 
vcrs  adultes,  frappes  du  memo  mal."  * 

Thus,  then  the  substance  of  the  egg  and  even  its  innermost 
vital  part,  is  permeable  by  a  parasite  sufficiently  large  to  be 
microscopically  visible.  It  is  also  of  course  permeable  by  the 
invisible  molecules  of  protein,  out  of  which  its  living  tissues  are 
formed,  and  by  absorption  of  which  they  subsequently  grow. 
But,  according  to  Weismann,  it  is  not  permeable  by  those 
invisible  units  of  protoplasm  out  of  which  the  vitally  active 
tissues  of  the  parent  are  constituted  :  units  composed,  as  we  must 
assume,  of  variously  arranged  molecules  of  protein.  So  that  the 
big  thing  may  pass,  and  the  little  thing  may  pass,  but  the  inter- 
mediate thing  may  not  pass  ! 

A  fact  of  kindred  nature,  unhappily  more  familiar,  may  be 
next  brought  in  evidence.  It  concerns  the  transmission  of  a 
disease  not  infrequent  among  those  of  unregulated  lives.  The 
highest  authority  concerning  this  disease,  in  its  inherited  form, 
is  Mr.  Jonathan  Hutchinson  ;  and  the  following  are  extracts 
from  a  letter  I  have  received  from  him,  and  which  I  publish  with 
his  assent  :  — 


"  I  do  not  think  that  there  can  be  any  reasonable  doubt  that  a  very  large 
majority  of  those  who  suffer  from  inherited  syphilis  take  the  taint  from  the 
male  parent.  ...  It  is  the  rule  when  a  man  marries  who  has  no 
remaining  local  lesion,  but  in  whom  the  taint  is  not  eradicated,  for  his  wife 
to  remain  apparently  well,  whilst  her  child  may  suffer.  No  doubt  the  child 
infects  its  mother's  blood,  but  this  does  not  usually  evoke  any  obvious 
symptoms  of  syphilis.  ...  I  am  sure  I  have  seen  hundreds  of  syphilitic 
infants  whose  mothers  had  not,  so  far  as  I  could  ascertain,  ever  displayed  a 
single  symptom." 

See,  then,  to  what  we  are  committed  if  we  accept  Weismann's 
hypothesis.  We  must  conclude,  that  whereas  the  reproductive 
cell  may  be  effectually  invaded  by  an  abnormal  living  element 
in  the  parental  organism,  those  normal  living  elements  which 
'  constitute  the  vital  protoplasm  of  the  parental  organism,  cannot 
invade  it.  Or  if  it  be  admitted  that  both  intrude,  then  the 
implication  is  that,  whereas  the  abnormal  element  can  so  modify 
the  development  as  to  cause  changes  of  structure  (as  of  the  teeth), 
the  normal  element  can  cause  no  changes  of  structure  !  f 

*  Les  Maladies  des  Vcrs  d  soic,  par  L.  Pasteur,  Vol.  I,  p.  39. 

f  Curiously  enough,  Weismann  refers  to,  and  recognizes,  syphilitic  infec- 


624  APPENDIX  B. 

We  pass  now  to  evidence  not  much  known  to  the  world  at 
large,  but  widely  known  in  the  biological  world,  though  known 
in  so  incomplete  a  manner  as  to  be  undervalued  in  it.  Indeed, 
when  I  name  it,  probably  many  will  vent  a  mental  pooh-pooh. 
The  fact  to  which  I  refer  is  one  of  which  record  is  preserved  in 
the  museum  of  the  College  of  Surgeons,  in  the  shape  of  paintings 
of  a  foal  borne  by  a  mare  not  quite  thoroughbred,  to  a  sire  which 
was  thoroughbred — a  foal  which  bears  the  markings  of  the 
quagga.  The  history  of  this  remarkable  foal  is  given  by  the 
Earl  of  Morton,  F.R.S.,  in  a  letter  to  the  President  of  the  Royal 
Society  (read  November  23,  1820).  In  it  he  states  that  wishing 
to  domesticate  the  quagga,  and  having  obtained  a  male  but  not  a 
female,  he  made  an  experiment. 

"  I  tried  to  breed  from  the  male  quagga  and  a  young  chestnut  mare  of 
seven-eighths  Arabian  blood,  and  which  had  never  been  bred  from;  the 
result  was  the  production  of  a  female  hybrid,  now  five  years  old,  and  bearing, 
both  in  her  form  and  in  her  colour,  very  decided  indications  of  her  mixed 
origin.  I  subsequently  parted  with  the  seven-eighths  Arabian  mare  to  Sir 
Gore  Ouseley,  who  has  bred  from  her  by  a  very  fine  black  Arabian  horse.  I 
yesterday  morning  examined  the  produce,  namely,  a  two-year-old  filly  and 
a  year-old  colt.  They  have  the  character  of  the  Arabian  breed  as  decidedlv 
as  can  be  expected,  where  fifteen-sixteenths  of  the  blood  are  Arabian ;  and 
they  are  fine  specimens  of  that  breed  ;  but  both  in  their  colour  and  in  the 
hair  of  their  manes,  they  have  a  striking  resemblance  to  the  quagga.  Their 
colour  is  bay,  marked  more  or  less  like  the  quagga  in  a  darker  tint.  Both 
are  distinguished  by  the  dark  line  along  the  ridge  of  the  back,  the  dark 
stripes  across  the  forehead,  and  the  dark  bars  across  the  back  part  of  the 
legs."  * 

Lord  Morton  then  names  sundry  further  correspondences. 
Dr.  Wollaston,  at  that  time  President  of  the  Royal  Society,  who 
had  seen  the  animals,  testified  to  the  correctness  of  his  de- 
scription, and,  as  shown  by  his  remarks,  entertained  no  doubt 
about  the  alleged  facts.  But  good  reason  for  doubt  may  be 

tion  of  the  reproductive  cells.  Dealing  with  Brown-Sequard's  cases  of 
inherited  epilepsy  (concerning  which,  let  me  say,  that  I  do  not  commit 
myself  to  any  derived  conclusions),  he  says : — "  In  the  case  of  epilepsy,  at 
any  rate,  it  is  easy  to  imagine  [many  of  Weismann's  arguments  are  based  on 
things  'it  is  easy  to  imagine']  that  the  passage  of  some  specific  organism 
through  the  reproductive  cells  may  take  place,  as  in  the  case  of  syphilis " 
(p.  82).  Here  is  a  sample  of  his  reasoning.  It  is  well  known  that  epilepsy 
is  frequently  caused  by  some  peripheral  irritation  (even  by  the  lodging  of  a 
small  foreign  body  under  the  skin),  and  that,  among  peripheral  irritations  . 
causing  it,  imperfect  healing  is  one.  Yet  though,  in  I.rown-Sequard's  cases, 
a  peripheral  irritation  caused  in  the  parent  by  local  injury  was  the  apparent 
origin,  Weismann  chooses  gratuitously  to  assume  that  the  progeny  were 
infected  by  "  some  specific  organism,"  which  produced  the  epilepsy  !  And 
then  though  the  epileptic  virus,  like  the  syphilitic  virus,  makes  itself  at  home 
in  the  e™,  the  parental  protoplasm  is  not  admitted  ! 

*  P,'alf>xo  >1tictd  TraTHutc'ion*  of  iJie  Royal  Society  for  tine  Year  1821,  Part  I, 
pp 


INADEQUACY   OF  NATURAL  SELECTION,   ETC.       C25 

assigned.  There  naturally  arises  the  question — How  does  it 
happen  that  parallel  results  are  not  observed  in  other  cases  ?  If 
in  any  progeny  certain  traits  not  belonging  to  the  sire,  but  be- 
longing to  a  sire  of  preceding  progeny,  are  reproduced,  how  is 
.it  that  such  anomalously  inherited  traits  are  not  observed  in 
domestic  animals,  and  indeed  in  mankind  ?  How  is  it  that  the 
children  of  a  widow  by  a  second  husband  do  not  bear  traceable 
resemblances  to  the  first  husband  ?  To  these  questions  nothing 
like  satisfactory  replies  seem  forthcoming ;  and,  in  the  absence  of 
replies,  scepticism,  if  not  disbelief,  may  be  held  reasonable. 

There  is  an  explanation,  however."  Forty  years  ago  I  made 
acquaintance  with  a  fact  which  impressed  me  by  its  significant 
implications,  and  has,  for  this  reason  I  suppose,  remained  in  my 
memory.  It  is  set  forth  in  the  Journal  of  the  Royal  Agricultural 
Society,  Vol.  XIV  (1853),  pp.  214  et  seq.,  and  concerns  certain 
results  of  crossing  French  and  English  breeds  of  sheep.  The 
writer  of  the  translated  paper,  M.  Malingie-Xouel,  Director  of  the 
Agricultural  School  of  La  Charmoise,  states  that  when  the  French 
breeds  of  sheep  (in  which  were  included  "  the  mongrel  Merinos  ") 
were  crossed  with  an  English  breed,  "  the  lambs  present  the  fol- 
lowing results.  Most  of  them  resemble  the  mother  more  than 
the  father ;  some  show  no  trace  of  the  father."  Joining  the 
admission  respecting  the  mongrels  with  the  facts  subsequently 
stated,  it  is  tolerably  clear  that  the  cases  in  which  the  lambs  bore 
no  traces  of  the  father  were  cases  in  which  the  mother  was  of  pure 
breed.  Speaking  of  the  results  of  these  crossings  in  the  second 
generation,  "having  75  per  cent,  of  English  blood,"  M.  Xouel 
says : — "  The  lambs  thrive,  wear  a  beautiful  appearance,  and  com- 
plete the  joy  of  the  breeder.  .  .  .  Xo  sooner  are  the  lambs 
weaned  than  their  strength,  their  vigour,  and  their  beauty  begin 
to  decay.  ...  At  last  the  constitution  gives  way  .  .  . 
lie  remains  stunted  for  life  :  "  the  constitution  being  thus  proved 
unstable  or  unadapted  to  the  requirements.  How,  then,  did 
M.  Xouel  succeed  in  obtaining  a  desirable  combination  of  a  fine 
English  breed  with  the  relatively  poor  French  breeds  ? 

He  took  an  animal  from  "flocks  originally  sprung  from  a  mixture  of  the 
two  distinct  races  that  are  established  in  those  two  provinces  [Berry  and 
La  Sologne],"  and  these  he  ''  united  with  animals  of  another  mixed  breed 
.  .  .  which  blended  the  Tourangelle  and  native  Merino  blood  of  "  La  Beaucc 
and  Tourainc,  and  obtained  a  mixture  of  all  four  races  "  without  decided 
character,  without  fixity  .  .  .  but  possessing  the  advantage  of  being  used  to 
our  climate  and  management." 

Putting  one  of  these  "  mixed  blood  ewes  to  a  pure  New-Kent  ram  .  .  . 
one  obtains  a  lamb  containing  fifty-hundredths  of  the  purest  and  most  ancient 
English  blood,  with  twelve  and  a  half  hundredths  of  four  different  French 
rapes,  which  are  individually  lost  in  the  preponderance  of  English  blood,  and 
disappear  almost  entirely,  leaving  the  improving  type  in  the  ascendant.  .  .  . 


626  APPENDIX  B. 

All  the  lambs  produced  strikingly  resembled  each  other,  and  even  Englishmen 
took  them  for  animals  of  their  own  country." 

M.  Nouel  goes  on  to  remark  that  when  this  derived  breed  was 
bred  with  itself,  the  marks  of  the  French  breeds  were  lost. 
"Some  slight  traces"  could  be  detected  by  experts,  but  these 
"  soon  disappeared." 

Thus  we  get  proof  that  relatively  pure  constitutions  predomi- 
nate in  progeny  over  mnch  mixed  constitutions.  The  reason  is 
not  difficult  to  see.  Every  organism  tends  to  become  adapted  to 
its  conditions  of  life ;  and  all  the  structures  of  a  species,  accus- 
tomed through  multitudinous  generations  to  the  climate,  food, 
and  various  influences  of  its  locality,  are  moulded  into  harmonious 
co-operation  favourable  to  life  in  that  locality  :  the  result  being 
that  in  the  development  of  each  young  individual,  the  tendencies 
conspire  to  produce  the  fit  organization.  It  is  otherwise  when 
the  species  is  removed  to  a  habitat  of  different  character,  or  when 
it  is  of  mixed  breed.  In  the  one  case  its  organs,  partially  out  of 
harmony  with  the  requirements  of  its  new  life,  become  partially 
out  of  harmony  with  one  another ;  since,  while  one  influence,  say 
of  climate,  is  but  little  changed,  another  influence,  say  of  food,  is 
much  changed ;  and,  consequently,  the  perturbed  relations  of  the 
organs  interfere  with  their  original  stable  equilibrium.  Still  more 
in  the  other  case  is  there  a  disturbance  in  equilibrium.  In  a 
mongrel,  the  constitution  derived  from  each  source  repeats  itself 
as  far  as  possible.  Hence  a  conflict  of  tendencies  to  evolve  two 
structures  more  or  less  unlike.  The  tendencies  do  not  harmoni- 
ously conspire,  but  produce  partially  incongruous  sets  of  organs. 
And  evidently  where  the  breed  is  one  in  which  there  are  united 
the  traits  of  various  lines  of  ancestry,  there  results  an  organiza- 
tion so  full  of  small  incongruities  of  structure  and  action,  that  it 
has  a  much-diminished  power  of  maintaining  its  balance;  and 
while  it  cannot  withstand  so  well  adverse  influences,  it  cannot  so 
well  hold  its  own  in  the  offspring.  Concerning  parents  of  pure 
and  mixed  breeds  respectively,  severally  tending  to  reproduce 
their  own  structures  in  progeny,  we  may  therefore  say,  figura- 
tively, that  the  house  divided  against  itself  cannot  withstand  the 
house  of  which  the  members  are  in  concord. 

Now  if  this  is  shown  to  be  the  case  with  breeds  the  purest  of 
which  have  been  adapted  to  their  habitats  and  modes  of  life  dur- 
ing some  few  hundred  years  only,  what  shall  we  say  when  the  ques- 
tion is  of  a  breed  which  has  had  a  constant  mode  of  life  in  the 
same  locality  for  ten  thousand  years  or  more,  like  the  quagga  ? 
In  this  the  stability  of  constitution  must  be  such  as  no  domestic 
animal  can  approach.  Relatively  stable  as  may  have  been  the 
constitutions  of  Lord  Morton's  horses,  as  compared  with  the  con- 
stitutions of  ordinary  horses,  yet,  since  Arab  horses,  even  in  their 


INADEQUACY  OP  NATURAL  SELECTION,  ETC.      G2Y 

native  country,  have  probably  in  the  course  of  successive  con- 
quests and  migrations  of  tribes  become  more  or  less  mixed,  and 
since  they  have  been  subject  to  the  conditions  of  domestic  life, 
differing  much  from  the  conditions  of  their  original  wild  life,  and 
since  the  English  breed  has  undergone  the  perturbing  effects  of 
change  from  the  climate  and  food  of  the  East  to  the  climate  and 
food  of  the  West,  the  organizations  of  the  horse  and  mare  in 
question  could  have  had  nothing  like  that  perfect  balance  pro- 
duced in  the  quagga  by  a  hundred  centuries  of  harmonious  co- 
operation. Hence  the  result.  And  hence  at  the  same  time  the 
interpretation  of  the  fact  that  analogous  phenomena  are  not 
obvious  among  most  domestic  animals,  or  among  ourselves  ;  since 
both  have  relatively  mixed,  and  generally  extremely  mixed,  con- 
stitutions, which,  as  we  see  in  ourselves,  have  been  made  genera- 
tion after  generation,  not  by  the  formation  of  a  mean  between 
two  parents,  but  by  the  jumbling  of  traits  of  the  one  with  traits 
of  the  other ;  until  there  exist  no  such  conspiring  tendencies 
among  the  parts  as  cause  repetition  of  combined  details  of  struc- 
ture in  posterity. 

Expectation  that  scepticism  might  be  felt  respecting  this  alleged 
anomaly  presented  by  the  quagga-marked  foal,  had  led  me  to 
think  over  the  matter ;  and  I  had  reached  this  interpretation 
before  sending  to  the  College  of  Surgeons  Museum  (being  unable 
to  go  myself)  to  obtain  the  particulars  and  refer  to  the  records. 
When  there  was  brought  to  me  a  copy  of  the  account  as  set  forth 
in  the  Philosophical  Transactions,  it  was  joined  with  the  informa- 
tion that  there  existed  an  appended  account  of  pigs,  in  which  a 
parallel  fact  had  been  observed.  To  my  immediate  inquiry — 
"  Was  the  male  a  wild  pig  ?  "  there  came  the  reply — "  I  did  not 
observe."  Of  course  I  forthwith  obtained  the  volume,  and  there 
found  what  I  expected.  It  was  contained  in  a  paper  communi- 
cated by  Dr.  Wollaston  from  Daniel  Giles,  Esq.,  concerning  his 
"  sow  and  her  produce,"  which  said  that — 

"  she  was  one  of  a  well-known  black  and  white  breed  of  Mr.  Western,  the 
Member  for  Essex.  About  ten  years  since  I  put  her  to  a  boar  of  the  wild 
breed,  and  of  a  deep  chestnut  colour  which  I  had  just  received  from 
Hatfield  House,  and  which  was  soon  afterwards  drowned  by  accident.  The 
pigs  produced  (which  were  her  first  litter)  partook  in  appearance  of  both 
boar  and  sow,  but  in  some  the  chestnut  colour  of  the  boar  strongly 
prevailed. 

"  The  sow  was  afterwards  put  to  a  boar  of  Mr.  Western's  breed  (the  wild 
boar  having  been  long  dead).  The  produce  was  a  litter  of  pigs,  some  of 
which,  we  observed  with  much  surprise,  to  be  stained  and  clearly  marked  with 
the  chestnut  colour  which  had  prevailed  in  the  former  litter." 

Mr.  Giles  adds  that  in  a  second  litter  of  pigs,  the  father  of  which 
was  of  Mr.  Western's  breed,  he  and  his  bailiff  believe  there  was  a 
recurrence,  in  some,  of  the  chestnut  colour,  but  admits  thai  their 


628  APPENDIX  B. 

"  recollection  is  much  less  perfect  than  I  wish  it  to  be."  lie  also 
adds  that,  in  the  course  of  many  years'  experience,  he  had  never 
known  the  least  appearance  of  the  chestnut  colour  in  Mr.  West- 
ern's breed. 

What  are  the  probabilities  that  these  two  anomalous  results 
should  have  arisen,  under  these  exceptional  conditions,  as  a 
matter  of  chance  ?  Evidently  the  probabilities  against  such  a 
coincidence  are  enormous.  The  testimony  is  in  both  cases  so 
good  that,  even  apart  from  the  coincidence,  it  would  be  unreason- 
able to  reject  it ;  but  the  coincidence  makes  acceptance  of  it  im- 
perative. There  is  mutual  verification,  at  the  same  time  that 
there  is  a  joint  interpretation  yielded  of  the  strange  phenomenon, 
and  of  its  non-occurrence  under  ordinary  circumstances. 

And  now,  in  presence  of  these  facts,  what  are  we  to  say  ? 
Simply  that  they  are  fatal  to  Weismann's  hypothesis.  They  show 
that  there  is  none  of  the  alleged  independence  of  the  reproductive 
cells ;  but  that  the  two  sets  of  cells  are  in  close  communion. 
They  prove  that  while  the  reproductive  cells  multiply  and  arrange 
themselves  during  the  evolution  of  the  embryo,  some  of  their 
germ-plasm  passes  into  the  mass  of  somatic  cells  constituting  the 
parental  body,  and  becomes  a  permanent  component  of  it.  Fur- 
ther, they  necessitate  the  inference  that  this  introduced  germ- 
plasm,  everywhere  diffused,  is  some  of  it  included  in  the  repro- 
ductive cells  subsequently  formed.  And  if  we  thus  get  a  demon- 
stration that  the  somewhat  different  units  of  a  foreign  germ-plasm 
permeating  the  organism,  permeate  also  the  subsequently  formed 
reproductive  cells,  and  affect  the  structures  of  the  individuals 
arising  from  them,  the  implication  is  that  the  like  happens  with 
those  native  units  which  have  been  made  somewhat  different  by 
modified  functions  :  there  must  be  a  tendency  to  inheritance  of 
acquired  characters. 

One  more  step  only  has  to  be  taken.  It  remains  to  ask  what 
is  the  flaw  in  the  assumption  with  which  Weismann's  theory  sets 
out.  If,  as  we  see,  the  conclusions  drawn  from  it  do  not  corre- 
spond to  the  facts,  then,  either  the  reasoning  is  invalid,  or  the 
original  postulate  is  untrue.  Leaving  aside  all  questions  con- 
cerning the  reasoning,  it  will  suffice  here  to  show  the  untruth  of 
the  postulate.  Had  his  work  been  written  during  the  early 
years  of  the  cell-doctrine,  the  supposition  that  the  multiplying 
cells  of  which  the  Metazoa  and  Metaphyta  are  composed,  become 
completely  separate,  could  not  have  been  met  by  a  reason- 
able scepticism  ;  but  now,  not  only  is  scepticism  justifiable,  but 
denial  is  called  for.  Some  dozen  years  ago  it  was  discovered  that 
in  many  cases  vegetal  cells  are  connected  with  one  another  by 


threads  of  protoplasm — threads  which  unite  the  internal  proto- 
plasm of  one  cell  w 


with  the  internal  protoplasms  of  cells  around 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      629 

It  is  as  though  the  pseudopodia  of  imprisoned  rhizopods  were 
fused  with  the  pseudopodia  of  adjacent  imprisoned  rhizopods. 
We  cannot  reasonably  suppose  that  the  continuous  network  of 
protoplasm  thus  constituted  has  heen  produced  after  the  cells 
have  become  adult.  These  protoplasmic  connections  must  have 
survived  the  process  of  fission.  The  implication  is  that  the  cells 
forming  the  embryo-plant  retained  their  protoplasmic  connections 
while  they  multiplied,  and  that  such  connections  continued 
throughout  all  subsequent  multiplications — an  implication  which 
has,  I  believe,  been  established  by  researches  upon  germinating 
palm- seeds.  But  now  we  come  to  a  verifying  series  of  facts 
which  the  cell-structures  of  animals  in  their  early  stages  present. 
In  his  Monograph  of  the  Development  of  Peripatus  Capensis,  Mr. 
Adam  Sedgwick,  F.R.S.,  Reader  in  Animal  Morphology  at  Cam- 
bridge, writes  as  follows  : — 

"  All  the  cells  of  the  ovum,  ectodermal  as  well  as  endodermal,  are  connected 
together  by  a  fine  protoplasmic  reticulum."  (p.  41) 

"  The  continuity  of  the  various  cells  of  the  segmenting  ovum  is  primary, 
and  not  secondary ;  i.  e.,  in  the  cleavage  the  segments  do  not  completely  sepa- 
rate from  one  another.  But  are  we  justified  in  speaking  of  cells  at  all  in  this 
case  ?  The  fully  segmented  ovum  is  a  syncytium,  and  there  are  not  and  have 
not  been  at  any  stage  cell  limits."  (p.  41) 

"  It  is  becoming  more  and  more  clear  every  day  that  the  cells  composing 
the  tissues  of  animals  are  not  isolated  units,  but  that  they  are  connected  with 
one  another.  I  need  only  refer  to  the  connection  known  to  exist  between 
connective  tissue  cells,  cartilage  cells,  epithelial  cells,  &c.  And  not  only  may 
the  cells  of  one  tissue  be  continuous  with  each  other,  but  they  may  also  be 
continuous  with  the  cells  of  other  tissues."  (pp.  47—8) 

"  Finally,  if  the  protoplasm  of  the  body  is  primitively  a  syncytium,  and  the 
ovum  until  maturity  a  part  of  that  syncytium,  the  separation  of  the  generative 
products  does  not  differ  essentially  from  the  internal  gemmation  of  a  Proto- 
zoon,  and  the  inheritance  by  the  offspring  of  peculiarities  first  appearing  in 
the  parent,  though  not  explained,  is  rendered  less  mysterious ;  for  the  proto- 
plasm of  the  whole  body  being  continuous,  change  in  the  molecular  constitu- 
tion of  any  part  of  it  would  naturally  be  expected  to  spread,  in  time,  through 
the  whole  mass."  (p.  49) 

Mr.  Sedgwick's  subsequent  investigations  confirm  these  conclu- 
sions. In  a  letter  of  December  27,  1892,  passages  which  he 
allows  me  to  publish  run  as  follows  : — 

"All  the  embryological  studies  that  I  have  made  since  that  to  which 
you  refer  confirm  me  more  and  more  in  the  view  that  the  connections 
between  the  cells  of  adults  are  not  secondary  connections,  but  primary,  dating 
from  the  time  when  the  embryo  was  a  unicellular  structure.  .  ."  .  My 
own  investigations  on  this  subject  have  been  confined  to  the  Arthropoda, 
Elasmobranchii,  and  Aves.  I  have  thoroughly  examined  the  development 
of  at  least  one  kind  of  each  of  these  groups,  and  I  have  never  been  able  to 
detect  a  stage  in  which  the  cells  were  not  continuous  with  each  other ; 
and  I  have  studied  innumerable  stages  from  the  beginning  of  cleavage 
onwards." 

So  that   the  alleged   independence  of,   the   reproductive  cells 
41 


630  APPENDIX  B. 

does  not  exist.  The  soma — to  use  Weismann's  name  for  the 
aggregate  of  cells  forming  the  body — is,  in  the  words  of  Mr. 
Sedgwick,  "  a  continuous  mass  of  vacuolated  protoplasm  ;  "  and 
the  reproductive  cells  are  nothing  more  than  portions  of  it  sepa- 
rated some  little  time  before  they  are  required  to  perform  their 
functions. 

Thus  the  theory  of  Weismann  is  doubly  disproved.  Induc- 
tively we  are  shown  that  there  does  take  place  that  communication 
of  characters  from  the  somatic  cells  to  the  reproductive  cells,  which 
he  says  cannot  take  place ;  and  deductively  we  are  shown  that 
this  communication  is  a  natural  sequence  of  connections  between 
the  two  which  he  ignores  ;  his  various  conclusions  are  deduced 
from  a  postulate  which  is  untrue. 

From  the  title  of  this  essay,  and  from  much  of  its  contents, 
nine  readers  out  of  ten  will  infer  that  it  is  directed  against  the 
views  of  Mr.  Darwin.  They  will  be  astonished  on  being  told 
that,  contrariwise,  it  is  directed  against  the  views  of  those  who,  in 
a  considerable  measure,  dissent  from  Mr.  Darwin.  For  the  in- 
heritance of  acquired  characters,  which  it  is  now  the  fashion  in 
the  biological  world  to  deny,  was,  by  Mr.  Darwin,  fully  recog- 
nized and  often  insisted  on.  Such  of  the  foregoing  arguments  as 
touch  Mr.  Darwin's  views,  simply  imply  that  the  cause  of  evolu- 
tion which  at  first  he  thought  unimportant,  but  the  importance 
of  which  he  increasingly  perceived  as  he  grew  older,  is  more 
important  than  he  admitted,  even  at  the  last.  The  neo-Darwin- 
ists,  however,  do  not  admit  this  cause  at  all. 

Let  it  not  be  supposed  that  this  explanation  implies  any  dis- 
approval of  the  dissentients,  considered  as  such.  Seeing  how 
little  regard  for  authority  I  have  myself  usually  shown,  it  would 
be  absurd  in  me  to  reflect  in  any  degree  upon  those  who  have 
rejected  certain  of  Mr.  Darwin's  teachings,  for  reasons  which  they 
have  held  sufficient.  But  while  their  independence  of  thought  is 
to  be  applauded  rather  than  blamed,  it  is,  I  think,  to  be  regretted 
that  they  have  not  guarded  themselves  against  a  long-standing 
bias.  It  is  a  common  trait  of  human  nature  to  seek  some 
excuse  when  found  in  the  wrong.  Invaded  self-esteem  sets  up  a 
defence,  and  anything  is  made  to  serve.  Thus  it  happened  that 
when  geologists  and  biologists,  previously  holding  that  all  kinds 
of  organisms  arose  by  special  creations,  surrendered  to  the 
battery  opened  upon  them  by  The  Origin  of  Species,  they  sought 
to  minimise  their  irrationality  by  pointing  to  irrationality  on  the 
other  side.  "  Well,  at  any  rate,  Lamarck  was  in  the  wrong." 
"  It  is  clear  that  we  were  right  in  rejecting  his  doctrine."  And 
so,  by  duly  emphasizing  the  fact  that  he  overlooked  "  Natural 
Selection  "  as  the  chief  cause,  and  by  showing  how  erroneous 


INADEQUACY  OF  NATURAL  SELECTION,  ETC.      631 

were  some  of  his  interpretations,  they  succeeded  in  mitigating 
the  sense  of  their  own  error.  It  is  true  their  creed  was  that  at 
successive  periods  in  the  Earth's  history,  old  Floras  and  Faunas 
had  been  abolished  and  others  introduced ;  just  as  though,  to  use 
Professor  Huxley's  figure,  the  table  had  been  now  and  again 
kicked  over  and  a  new  pack  of  cards  brought  out.  And  it  is 
true  that  Lamarck,  while  he  rejected  this  absurd  creed,  assigned 
for  the  facts  reasons  some  of  which  are  absurd.  But  in  conse- 
quence of  the  feeling  described,  his  defensible  belief  was  for- 
gotten and  only  his  indefensible  ones  remembered.  This  one- 
sided estimate  has  become  traditional ;  so  that  there  is  now  often 
shown  a  subdued  contempt  for  those  who  suppose  that  there  can  ' 
be  any  truth  in  the  reasonings  of  a  man  whose  general  concep- 
tion was  partly  sense,  at  a  time  when  the  general  conceptions  of 
his  contemporaries  were  wholly  nonsense.  Hence  results  unfair 
treatment — hence  result  the  different  dealings  with  the  views  of 
Lamarck  and  of  Weismann. 

"  Where  are  the  facts  proving  the  inheritance  of  acquired 
characters  ? "  ask  those  who  deny  it.  Well,  in  the  first  place, 
there  might  be  asked  the  counter-question — Where  are  the  facts 
which  disprove  it  ?  Surely  if  not  only  the  general  structures  of 
organisms,  but  also  many  of  the  modifications  arising  in  them, 
are  inheritable,  the  natural  implication  is  that  all  modifications 
are  inheritable ;  and  if  any  say  that  the  inheritableness  is  limited 
to  those  arising  in  a  certain  way,  the  onus  lies  on  them  of  proving 
that  those  otherwise  arising  are  not  inheritable.*  Leaving  this 
counter-question  aside,  however,  it  will  suffice  if  we  ask  another 
counter-question.  It  is  asserted  that  the  dwindling  of  organs 
from  disuse  is  due  to  the  successive  survivals  in  posterity  of 
individuals  in  which  the  organs  have  varied  in  the  direction  of 

*  It  will,  I  suppose,  be  said  that  the  non- inheritance  of  mutilations  consti- 
tutes evidence  of  the  kind  here  asked  for.  The  first  reply  is  that  the  evidence 
is  conflicting,  as  it  may  well  be.  It  is  forgotten  that  to  have  valid  evidence 
of  non-inheritance  of  mutilations,  it  is  requisite  that  both  parents  shall  have 
undergone  mutilation,  and  that  this  does  not  often  happen.  If  they  have  not, 
then,  assuming  the  inheritableness  of  mutilations,  there  would,  leaving  out 
other  causes,  be  an  equal  tendency  to  appearance  and  non-appearance  of  the 
mutilation  in  offspring.  But  there  is  another  cause— the  tendency  to  rever- 
sion, which  ever  works  in  the  direction  of  cancelling  individual  characters 
by  the  return  to  ancestral  characters.  So  that  even  were  the  inheritance  of 
mutilations  to  be  expected  (and  for  myself  I  may  say  that  its  occurrence  sur- 
prises me),  it  could  not  be  reasonably  looked  for  as  more  than  exceptional : 
there  are  two  strong  countervailing  tendencies.  But  now,  in  the  second  place, 
let  it  be  remarked  that  the  inheritance  or  non-inheritance  of  mutilations  is* 
beside  the  question.  The  question  is  whether  modifications  of  parts  pro- 
duced by  modifications  of  functions  are  inheritable  or  not.  And  then,  by  way 
of  disproof  of  their  inheritableness,  we  are  referred  to  cases  in  which  the 
modifications  of  parts  arc  not  produced  by  modifications  of  functions,  but  are 
otherwise  produced ! 


T,32  APPENDIX  B. 

decrease.  Where  now  are  the  facts  supporting  this  assertion  ? 
Not  one  has  been  assigned  or  can  be  assigned.  Not  a  single  case 
can  be  named  in  which  panmixia  is  a  proved  cause  of  diminution. 
Even  had  the  deductive  argument  for  panmixia  been  as  valid 
as  we  have  found  it  to  be  invalid,  there  would  still  have  been 
required,  in  pursuance  of  scientific  method,  some  verifying  in- 
ductive evidence.  Yet,  though  not  a  shred  of  such  evidence 
has  been  given,  the  doctrine  is  accepted  with  acclamation,  and 
adopted  as  part  of  current  biological  theory.  Articles  are  writ- 
ten and  letters  published  in  which  it  is  assumed  that  this  mere 
speculation,  justified  by  not  a  tittle  of  proof,  displaces  large  con- 
clusions previously  drawn.  And  then,  passing  into  the  outer 
world,  this  unsupported  belief  affects  opinions  there  too ;  so  that 
we  have  recently  had  a  Right  Honourable  lecturer  who,  taking 
for  granted  its  truth,  represents  the  inheritance  of  acquired  char- 
acters as  an  exploded  hypothesis,  and  proceeds  to  give  revised 
views  of  human  affairs. 

Finally,  there  comes  the  reply  that  there  are  facts  proving  the 
inheritance  of  acquired  characters.  All  those  assigned  by  Mr. 
Darwin,  together  writh  others  such,  remain  outstanding  when  we 
find  that  the  interpretation  by  panmixia  is  untenable.  Indeed, 
even  had  that  hypothesis  been  tenable,  it  would  have  been  inap- 
plicable to  these  cases ;  since  in  domestic  animals,  artificially  fed 
and  often  overfed,  the  supposed  advantage  from  economy  cannot 
be  shown  to  tell ;  and  since,  in  these  cases,  individuals  are  not 
naturally  selected  during  the  struggle  for  life,  in  which  certain 
traits  are  advantageous,  but  are  artificially  selected  by  man  with- 
out regard  to  such  traits.  Should  it  be  urged  that  the  assigned 
facts  are  not  numerous,  it  may  be  replied  that  there  are  no  per- 
sons whose  occupations  and  amusements  incidentally  bring  out 
such  facts ;  and  that  they  are  probably  as  numerous  as  those 
which  would  have  been  available  for  Mr.  Darwin's  hypothesis, 
had  there  been  no  breeders  and  fanciers  and  gardeners  who,  in 
pursuit  of  their  profits  and  hobbies,  furnished  him  with  evidence. 
It  may  be  added  that  the  required  facts  are  not  likely  to  be 
numerous,  if  biologists  refuse  to  seek  for  them. 

See,  then,  how  the  case  stands.  Natural  selection,  or  survival 
of  the  fittest,  is  almost  exclusively  operative  throughout  the 
vegetal  world  and  throughout  the  lower  animal  world,  charac- 
terized by  relative  passivity.  But  with  the  ascent  to  higher 
types  of  animals,  its  effects  are  in  increasing  degrees  involved 
with  those  produced  by  inheritance  of  acquired  characters; 
until,  in  animals  of  complex  structures,  inheritance  of  acquired 
characters  becomes  an  important,  if  not  the  chief,  cause  of  evo- 
lution. We  have  seen  that  natural  selection  cannot  work  any 
changes  in  organisms  save  such  as  conduce  in  considerable 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.       623 

degrees,  directly  or  indirectly,  to  the  multiplication  of  the  stirp  ; 
whence  failure  to  account  for  various  changes  ascribed  to  it. 
And  we  have  seen  that  it  yields  no  explanation  of  the  co-adapta- 
tion of  co-operative  parts,  even  when  the  co-operation  is  rela- 
tively simple,  and  still  less  when  it  is  complex.  On  the  other 
hand,  we  see  that  if,  along  with  the  transmission  of  generic  and 
specific  structures,  there  tend  to  be  transmitted  modifications 
arising  in  a  certain  way,  there  is  a  strong  a  priori  probability  that 
there  tend  to  be  transmitted  modifications  arising  in  all  ways. 
We  have  a  number  of  facts  confirming  this  inference,  and  show- 
ing that  acquired  characters  are  inherited— as  large  a  number  as 
can  be  expected,  considering  the  difficulty  of  observing  them  and 
the  absence  of  search.  And  then  to  these  facts  may  be  added 
the  facts  with  which  this  essay  set  out,  concerning  the  distribu- 
tion of  tactual  discriminativeness.  AA'hile  we  saw  that  these  are 
inexplicable  by  survival  of  the  fittest,  we  saw  that  they  are 
clearly  explicable  as  resulting  from  the  inheritance  of  acquired 
characters.  And  here  let  it  be  added  that  this  conclusion  is  con- 
spicuously warranted  by  one  of  the  methods  of  inductive  logic, 
known  as  the  method  of  concomitant  variations.  For  throughout 
the  whole  series  of  gradations  in  perceptive  power,  we  saw  that 
the  amount  of  the  effect  is  proportionate  to  the  amount  of  the 
alleged  cause. 


II. 

Apart  from  those  more  special  theories  of  Professor  Weismann 
I  lately  dealt  with,  the  wide  acceptance  of  which  by  the  biological 
world  greatly  surprises  me,  there  are  certain  more  general  theo- 
ries of  his — fundamental  theories — the  acceptance  of  which 
surprises  me  still  more.  Of  the  two  on  which  rests  the  vast 
superstructure  of  his  speculations,  the  first  concerns  the  distinc- 
tion between  the  reproductive  elements  of  each  organism  and 
the  non-reproductive  elements,  lie  says  : — 

"  Let  us  now  consider  how  it  happened  that  the  raulticellular  animals  and 
plants,  which  arose  from  unicellular  forms  of  life,  came  to  lose  this  power  of 
living  for  ever. 

"The  answer  to  this  question  is  closely  bound  up  with  the  principle  of 
division  of  labour  which  appeared  among  multicellular  organisms  at  a  very 
early  stage. 

"  The  first  multicellular  organism  was  probably  a  cluster  of  similar  cells, 
but  these  units  soon  lost  their  oriirinal  homogeneity.  As  the  result  of  mere 
relative  position,  some  of  the  cells  were  especially  fitted  to  provide  for  the 
nutrition  of  the  colony,  while  others  undertook  the  work  of  reproduction." 
(Essays  upon  Heredity,  i,  p.  27) 

Here,  then,  we  have  the  great  principle  of  the  division  of 
labour,  which  is  the  principle  of  all  organization,  taken  as  prima- 


634  APPENDIX  B. 

rily  illustrated  in  the  division  between  the  reproductive  cells  and 
the  non-reproductive  or  somatic  cells — the  cells  devoted  to  the 
continuance  of  the  species,  and  the  cells  which  subserve  the  life 
of  the  individual.  And  the  early  separation  of  reproductive  cells 
from  somatic  cells,  is  alleged  on  the  ground  that  this  primary 
division  of  labour  is  that  which  arises  between  elements  devoted 
to  species-life  and  elements  devoted  to  individual  life.  Let  us 
not  be  content  with  words  but  look  at  the  facts. 

When  Milne-Edwards  first  used  the  phrase  "  physiological 
division  of  labour,"  he  was  obviously  led  to  do  so  by  perceiving 
the  analogy  between  the  division  of  labour  in  a  society,  as 
described  by  political  economists,  and  the  division  of  labour  in  an 
organism.  Every  one  who  reads  has  been  familiarized  with  the 
first  as  illustrated  in  the  early  stages,  when  men  were  warriors 
while  the  cultivation  and  drudgery  were  done  by  slaves  and 
women  ;  and  as  illustrated  in  the  later  stages,  when  not  only  are 
agriculture  and  manufactures  carried  on  by  separate  classes,  but 
agriculture  is  carried  on  by  landlords,  farmers,  and  labourers, 
while  manufactures,  multitudinous  in  their  kinds,  severally  in- 
volve the  actions  of  capitalists,  overseers,  workers,  <fcc.,  and 
while  the  great  function  of  distribution  is  carried  on  by  whole- 
sale and  retail  dealers  in  different  commodities.  Meanwhile 
students  of  biology,  led  by  Milne-Edwards's  phrase,  have  come 
to  recognize  a  parallel  arrangement  in  a  living  creature  ;  shown, 
primarily,  in  the  devoting  of  the  outer  parts  to  the  general 
business  of  obtaining  food  and  escaping  from  enemies,  while  the 
inner  parts  are  devoted  to  the  utilization  of  food,  and  supporting 
themselves  and  the  outer  parts ;  and  shown,  secondarily,  by  the 
subdivision  of  these  great  functions  into  those  of  various  limbs 
and  senses  in  the  one  case,  and  in  the  other  case  into  those  of 
organs  for  digestion,  respiration,  circulation,  excretion,  <fec.  But 
now  let  us  ask  what  is  the  essential  nature  of  this  division  of 
labour.  In  both  cases  it  is  an  exchange  of  services — an  arrange- 
ment under  which,  while  one  part  devotes  itself  to  one  kind  of 
action  and  yields  benefits  to  all  the  rest,  all  the  rest,  jointly  and 
severally  performing  their  special  actions,  yield  benefits  to  it  in 
exchange.  Otherwise  described,  it  is  a  system  of  mutual  depen- 
dence :  A  depends  for  its  welfare  upon  B,  C,  and  D  ;  B  upon  A, 
C,  and  D  ;  and  so  with  the  rest :  all  depend  upon  each  and  each 
upon  all.  Now  let  us  apply  this  true  conception  of  the  division 
of  labour,  to  that  which  Professor  Weismann  calls  a  division  of 
labour.  Where  is  the  exchange  of  services  between  somatic  cells 
and  reproductive  cells  ?  There  is  none.  The  somatic  cells  render 
great  services  to  the  reproductive  cells,  by  furnishing  them  with 
materials  for  growth  and  multiplication  ;  but  the  reproductive 
cells  render  no  services  at  all  to  the  somatic  cells.  If  we  look 


INADEQUACY  OP  NATURAL  SELECTION,   ETC.       635 

for  the  mutual  dependence  we  look  in  vain.  We  find  entire 
dependence  on  the  one  side  and  none  on  the  other.  Between  the 
parts  devoted  to  individual  life  and  the  part  devoted  to  species- 
life,  there  is  no  division  of  labour  whatever.  The  individual 
works  for  the  species  ;  but  the  species  works  not  for  the  indivi- 
dual. Whether  at  the  stage  when  the  species  is  represented  by 
reproductive  cells,  or  at  the  stage  when  it  is  represented  by  eggs, 
or  at  the  stage  when  it  is  represented  by  young,  the  parent  does 
everything  for  it,  and  it  does  nothing  for  the  parent.  The 
essential  part  of  the  conception  is  gone  :  there  is  no  giving  and 
receiving,  no  exchange,  no  mutuality, 

But  now  suppose  we  pass  over  this  fallacious  interpretation, 
and  grant  Professor  Weismann  his  fundamental  assumption  and 
his  fundamental  corollary.  Suppose  we  grant  that  because  the 
primary  division  of  labour  is  that  between  somatic  cells  and 
reproductive  cells,  these  two  groups  are  the  first  to  be  differen- 
tiated. Having  granted  this  corollary,  let  us  compare  it  with 
the  facts.  As  the  alleged  primary  division  of  labour  is  universal, 
so  the  alleged  primary  differentiation  should  be  universal  too. 
Let  us  see  whether  it  is  so.  Already,  in  the  paragraph  from 
which  I  have  quoted  above,  a  crack  in  the  doctrine  is  admitted  : 
it  is  said  that  "  this  differentiation  was  not  at  first  absolute,  and 
indeed  it  is  not  always  so  to-day."  And  then,  on  turning  to 
page  74,  we  find  that  the  crack  has  become  a  chasm.  Of  the 
reproductive  cells  it  is  stated  that — "  In  Vertebrata  they  do  not 
become  distinct  from  the  other  cells  of  the  body  until  the  embryo 
is  completely  formed."  That  is  to  say,  in  this  large  and  most 
important  division  of  the  animal  kingdom,  the  implied  universal 
law  does  not  hold.  Much  more  than  this  is  confessed.  Lower 
down  the  page  we  read — "  There  may  be  in  fact  cases  in  which 
such  separation  does  not  take  place  until  after  the  animal  is  com- 
pletely formed,  and  others,  as  I  believe  that  I  have  shown,  in 
which  it  first  arises  one  or  more  generations  later,  viz.,  in  the  buds 
produced  by  the  parent." 

So  that  in  other  great  divisions  of  the  animal  kingdom  the 
alleged  law  is  broken  ;  as  among  the  Coelenterata  by  the  Jfydrozoa, 
as  among  the  Mollusca  by  the  Ascidians,  and  as  among  the 
Platyhelminthes  by  the  Trematode  worms. 

Following  this  admission  concerning  the  Vertebrata,  come 
certain  sentences  which  I  partially  italicize  : — 

"Thus,  as  their  development  shows,  a  marked  antithesis  exists  between 
the  substance  of  the  undying  reproductive  cells  and  that  of  the  perishable 
body-cells.  We  cannot  explain  this  fact  except  by  the  supposition  that  each 
reproductive  cell  potentially  contains  two  kinds  of  substance,  which  at  a 
variable  time  after  the  commencement  of  embryonic  development,  separate 
from  one  another,  and  finally  produce  two  sharply  contrasted  groups  of  cells." 
(p.  74) 


836  APPENDIX  B. 

And  a  little  lower  down  the  page  we  meet  with  the  lines  : — 
"  It  is  therefore  quite  conc<ivab'e  thai,  the  reproductive  cells  might  sepa- 
rate  from   the   somatic   cells   much  later  than  in  the  examples  mentioned 
sibove,  without   changing   the   hereditary  tendencies   of  which   they  are  the 
bearers." 

That  is  to  say,  it  is  "  quite  conceivable "  that  after  sexless 
Cercarice  have  gone  on  multiplying  by  internal  gemmation  for 
generations,  the  "  two  kinds  of  substance  "  have,  notwithstanding 
innumerable  cell-divisions,  preserved  their  respective  natures,  and 
finally  separate  in  such  ways  as  to  produce  reproductive  cells. 
Here  Professor  Weismann  does  not,  as  in  a  case  before  noted, 
assume  something  which  it  is  "  easy  to  imagine,"  but  he  assumes 
something  which  it  is  difficult  to  imagine  ;  and  apparently  thinks 
that  a  scientific  conclusion  may  be  thereon  safely  based. 

Associated  with  the  assertion  that  the  primary  division  of 
labour  is  between  the  somatic  cells  and  the  reproductive  cells, 
and  associated  with  the  corollary  that  the  primary  differentiation 
is  that  which  arises  between  them,  there  goes  another  corollary. 
It  is  alleged  that  there  exists  a  fundamental  distinction  of  nature 
between  these  two  classes  of  cells.  They  are  described  as  respec- 
tively mortal  and  immortal,  in  the  sense  that  those  of  the  one 
class  are  limited  in  their  powers  of  multiplication,  while  those  of 
the  other  class  are  unlimited.  And  it  is  contended  that  this  is 
due  to  inherent  unlikeness  of  nature. 

Before  inquiring  into  the  truth  of  this  proposition,  I  may  fitly 
remark  upon  a  preliminary  proposition  set  down  by  Professor 
Weismann.  Referring  .to  the  hypothesis  that  death  depends 
"  upon  causes  which  lie  in  the  nature  of  life  itself,"  he  says : — 

"  I  do  not  however  believe  in  the  validity  of  this  explanation :  I  consider 
that  death  is  not  a  primary  necessity,  but  that  it  has  been  secondarily  acquired 
as  an  adaptation.  I  believe  that  life  is  endowed  with  a  fixed  duration,  not 
because  it  is  contrary  to  its  nature  to  be  unlimited,  but  because  the  unlimited 
existence  of  individuals  would  be  a  luxury  without  any  corresponding  advan- 
tage." (p.  24) 

This  last  sentence  has  a  teleological  sound  which  would  be 
appropriate  did  it  come  from  a  theologian,  but  which  seems 
strange  as  coming  from  a  man  of  science.  Assuming,  however, 
that  the  implication  was  not  intended,  I  go  on  to  remark  that 
Professor  Weismann  has  apparently  overlooked  a  universal  law 
of  evolution — not  organic  only,  but  inorganic  and  super-organic 
— which  implies  the  necessity  of  death.  The  changes  of  every 
aggregate,  no  matter  of  what  kind,  inevitably  end  in  a  state  of 
equilibrium.  Suns  and  planets  die,  as  well  as  organisms.  The 
process  of  integration,  which  constitutes  the  fundamental  trait  of 
all  evolution,  continues  until  it  has  brought  about  a  state  which 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      637 

negatives  further  alterations,  molar  or  molecular — a  state  of 
balance  among  the  forces  of  the  aggregate  and  the  forces  which 
oppose  them/"  In  so  far,  therefore,  as  Professor  Weismann's 
conclusions  imply  the  non-necessity  of  death,  they  cannot  be 
sustained. 

But  now  let  us  consider  the  above-described  antithesis  be- 
tween the  immortal  Protozoa  and  the  mortal  Metazoa,  An  essen- 
tial part  of  the  theory  is  that  the  Protozoa  can  go  on  dividing 
and  subdividing  without  limit,  so  long  as  the  fit  external  condi- 
tions are  maintained.  But  what  is  the  evidence  for  this  ?  Even 
by  Professor  Weismann's  own  admission  there  is  no  proof.  On 
p.  285  he  says  : — 

"  I  could  only  consent  to  adopt  the  hypothesis  of  rejuvenescence  [achieved 
by  conjugation],  if  it  were  rendered  absolutely  certain  that  reproduction  by 
division  could  never  under  any  circumstances  persist  indefinitely.  But  this 
cannot  be  proved  with  any  greater  certainty  than  the  converse  proposition, 
and  hence,  as  far  as  direct  proof  is  concerned,  the  facts  are  equally  uncertain 
on  both  sides." 

But  this  is  an  admission  which  seems  to  be  entirely  ignored 
when  there  is  alleged  the  contrast  between  the  immortal  Protozoa 
and  the  mortal  Metazoa.  Following  Professor  Weismann's  method, 
it  would  be  "  easy  to  imagine  "  that  occasional  conjugation  is  in 
all  cases  essential ;  and  this  easily  imagined  conclusion  might  fitly 
be  used  to  bar  out  his  own.  Indeed,  considering  how  commonly 
conjugation  is  observed,  it  may  be  held  difficult  to  imagine  that 
it  can  in  any  cases  be  dispensed  with.  Apart  from  imaginations 
of  either  kind,  however,  here  is  an  acknowledgment  that  the 
immortality  of  Protozoa  is  not  proved ;  that  the  allegation  has  no 
better  basis  than  the  failure  to  observe  cessation  of  fission ;  and 
that  thus  one  term  of  the  above  antithesis  is  not  a  fact,  but  is 
only  an  assumption. 

And  now  what  about  the  other  term  of  the  antithesis— the 
alleged  inherent  mortality  of  the  somatic  cells  ?  This  we  shall,  I 
think,  find  is  no  more  defensible  than  the  other.  Such  plausi- 
bility as  it  possesses  disappears  when,  instead  of  contemplating 
the  vast  assemblage  of  familiar  cases  which  animals  present,  we 
contemplate  certain  less  familiar  and  unfamiliar  cases.  By  these 
we  are  shown  that  the  usual  ending  of  multiplication  among 
somatic  cells  is  due,  not  to  an  intrinsic  cause,  but  to  extrinsic 
causes.  Let  us,  however,  first  look  at  Professor  Weismann's 
own  statements : — 

"  I  have  endeavoured  to  explain  death  as  the  result  of  restriction  in  the 
powers  of  reproduction  possessed  by  the  somatic  cells,  and  I  have  suggested 
that  such  restriction  may  conceivably  follow  from  a  limitation  in  the 

*  Sec  First  Principles,  Part  II,  Chap.  XXII,  "  Equilibration." 


638  APPENDIX  B. 

number  of  cell-generations  possible  for  the  cells  of  each  organ  and  tissue." 
(p.  28) 

"  The  above-mentioned  considerations  show  us  that  the  degree  of  repro- 
ductive activity  present  in  the  tissues  is  regulated  by  internal  pauses  while  the 
natural  death  of  an  organism  is  the  termination — the  hereditary  limitation — 
of  the  process  of  cell-division,  which  began  in  the  segmentation  of  the  ovum." 
(p.  30) 

Now,  though,  in  the  above  extracts  there  is  mention  of  "  in- 
ternal causes  "  determining  "  the  degree  of  reproductive  activity  " 
of  tissue  cells,  and  though,  on  page  28,  the  "causes  of  the  loss" 
of  the  power  of  unlimited  cell-production  "  must  be  sought  out- 
side the  organism,  that  is  to  say,  in  the  external  conditions  of 
life,"  yet  the  doctrine  is  that  somatic  cells  have  become  consti- 
tutionally unfitted  for  continued  cell-multiplication. 

"  The  somatic  cells  have  lost  this  power  to  a  gradually  increasing  extent,  so 
that  at  length  they  became  restricted  to  a  fixed,  though  perhaps  very  large, 
number  of  cell-generations."  (p.  28) 

Examination  will  soon  disclose  good  reasons  for  denying  this  in- 
herent restriction.  We  will  look  at  the  various  causes  which 
affect  their  multiplication,  and  usually  put  a  stop  to  increase  after 
a  certain  point  is  reached. 

There  is  first  the  amount  of  vital  capital  given  by  the  parent ; 
partly  in  the  shape  of  a  more  or  less  developed  structure,  and 
partly  in  the  shape  of  bequeathed  nutriment.  Where  this  vital 
capital  is  small,  and  the  young  creature,  forthwith  obliged  to 
carry  on  physiological  business  for  itself,  has  to  expend  effort  in 
obtaining  materials  for  daily  consumption  as  well  as  for  growth, 
a  rigid  restraint  is  put  on  that  cell-multiplication  required  for  a 
large  size.  Clearly,  the  young  elephant,  starting  with  a  big  and 
well-organized  body,  and  supplied  gratis  with  milk  during  early 
stages  of  growth,  can  begin  physiological  business  on  his  own 
account  on  a  great  scale ;  and  by  its  large  transactions  his  system 
is  enabled  to  supply  nutriment  to  its  multiplying  somatic  cells 
until  they  have  formed  a  vast  aggregate— an  aggregate  such  as 
it  is  impossible  for  a  young  mouse  to  reach,  obliged  as  it  is  to 
begin  physiological  business  in  a  small  way.  Then  there  is  the 
character  of  the  food  in  respect  of  its  digestibility  and  its  nutri- 
tiveness.  Here,  that  which  the  creature  takes  in  requires  much 
grinding-up,  or,  when  duly  prepared,  contains  but  a  small  amount 
of  available  matter  in  comparison  with  the  matter  that  has  to  be 
thrown  away ;  while  there,  the  prey  seized  is  almost  pure  nutri- 
ment, and  requires  but  little  trituration.  Hence,  in  some  cases, 
an  unprofitable  physiological  business,  and  in  other  cases  a  profit- 
able one ;  resulting  in  small  or  large  supplies  to  the  multiplying 
somatic  cells.  Further,  there  has  to  be  noted  the  grade  of 
visceral  development,  which,  if  low,  yields  only  crude  nutriment 
slowly  distributed,  but  which,  if  high,  serves  by  its  good  appli- 


INADEQUACY  OP  NATURAL  SELECTION,  ETC.      639 

ances  for  solution,  depuration,  absorption,  and  circulation,  to 
yield  to  the  multiplying-  somatic  cells  a  rich  and  pure  blood. 
Then  we  come  to  an  all-important  factor,  the  cost  of  obtaining 
food.  Here  large  expenditure  of  energy  in  locomotion  is  necessi- 
tated, and  there  but  little — here  great  efforts  for  small  portions 
of  food,  and  there  small  efforts  for  great  portions  :  again  result- 
ing in  physiological  poverty  or  physiological  wealth.  Next, 
beyond  the  cost  of  nervo-muscular  activities  in  foraging,  there  is 
the  cost  of  maintaining  bodily  heat.  So  much  heat  implies  so 
much  consumed  nutriment,  and  the  loss  by  radiation  or  conduc- 
tion, which  has  perpetually  to  be  made  good,  varies  according  to 
many  circumstances — climate,  medium  (as  air  or  water),  covering, 
size  of  body  (small  cooling  relatively  faster  than  large) ;  and  in 
proportion  to  the  cost  of  maintaining  heat  is  the  abstraction  from 
the  supplies  for  cell-formation.  Finally,  there  are  three  all- 
important  co-operative  factors,  or  rather  laws  of  factors,  the 
effects  of  which  vary  with  the  size  of  the  animal.  The  first  is 
that,  while  the  mass  of  the  body  varies  as  the  cubes  of  its  dimen- 
sions (proportions  being  supposed  constant),  the  absorbing  surface 
varies  as  the  squares  of  its  dimensions ;  whence  it  results  that, 
other  things  equal,  increase  of  size  implies  relative  decrease  of 
nutrition,  and  therefore  increased  obstacles  to  cell-multiplication.* 
The  second  is  a  further  sequence  from  these  laws — namely,  that 
while  the  weight  of  the  body  increases  as  the  cubes  of  the  dimen- 
sions, the  sectional  areas  of  its  muscles  and  bones  increase  as 
their  squares  ;  whence  follows  a  decreasing  power  of  resisting 
strains,  and  a  relative  weakness  of  structure.  This  is  implied  in 
the  ability  of  a  small  animal  to  leap  many  times  its  own  length, 
while  a  great  animal,  like  the  elephant,  cannot  leap  at  all :  its 
bones  and  muscles  being  unable  to  bear  the  stress  which  would 
be  required  to  propel  its  body  through  the  air.  What  increasing 
cost  of  keeping  together  the  bodily  fabric  is  thus  entailed, 
we  cannot  say ;  but  that  there  is  an  increasing  cost,  which 
diminishes  the  available  materials  for  increase  of  size,  is  beyond 
question,  f  And  then,  in  the  third  place,  we  have  augmented 
expense  of  distribution  of  nutriment.  The  greater  the  size 
becomes,  the  more  force  must  be  exerted  to  send  blood  to  the 
periphery  ;  and  this  once  more  entails  deduction  from  the  cell- 
forming  matters. 

*  Principles  of  Biology,  §  46,  (No.  8.  April,  1863). 

f  Ibid.  This  must  not  be  understood  as  implying  that  while  the  mass 
increases  as  the  cubes,  the  quantity  of  motion  which  can  be  generated  increases 
only  as  the  squares ;  for  this  would  not  be  true.  The  quantity  of  motion  is 
obviously  measured,  not  by  the  sectional  areas  of  the  muscles  alone,  but  by 
these  multiplied  into  their  lengths,  and  therefore  increases  as  the  cubes.  But 
this  admission  leaves  untouched  the  conclusion  that  the  ability  to  bear  stress 
increases  only  as  the  squares ;  and  thus  limits  the  ability  to  generate  motion, 
by  relative  incoherence  of  materials. 


640  APPENDIX  B. 

Here,  then,  we  have  nine  factors,  several  of  them  involving 
subdivisions,  which  co-operate  in  aiding  or  restraining  cell- 
multiplication.  They  occur  in  endlessly  varied  proportions  and 
combinations ;  so  that  every  species  differs  more  or  less  from 
every  other  in  respect  of  their  effects.  But  in  all  of  them  the 
co-operation  is  such  as  eventually  arrests  that  multiplication  of 
cells  which  causes  further  growth ;  continues  thereafter  to  entail 
slow  decrease  in  cell-multiplication,  accompanying  decline  of 
vital  activities  ;  and  eventually  brings  cell-multiplication  to  an 
end.  Now  a  recognized  principle  of  reasoning — the  Law  of 
Parsimony — forbids  the  assumption  of  more  causes  than  are 
needful  for  explanation  of  phenomena ;  and  since,  in  all  such 
living  aggregates  as  those  above  supposed,  the  causes  named 
inevitably  bring  about  arrest  of  cell-multiplication,  it  is  illegiti- 
mate to  ascribe  this  arrest  to  some  inherent  property  in  the  cells. 
Inadequacy  of  the  other  causes  must  be  shown  before  an  inherent 
property  can  be  rightly  assumed. 

For  this  conclusion  we  find  ample  justification  when  we  con- 
template types  of  animals  which  lead  lives  that  do  not  put  such 
decided  restraints  on  cell-multiplication.  First  let  us  take  an 
instance  of  the  extent  to  which  (irrespective  of  natures  of  cells  as 
reproductive  or  somatic)  cell-multip.ication  may  go,  where  the 
conditions  render  nutrition  easy  and  reduce  expenditure  to  a 
minimum.  I  refer  to  the  case  of  the  Aphides.  Though  it  is 
early  in  the  season  (March),  the  hothouses  at  Kew  have  furnished 
a  sufficient  number  of  these  to  show  that  twelve  of  them  weigh 
a  grain — a  larger  number  than  would  be  required  were  they  full- 
sized.  Citing  Professor  Owen,  who  adopts  the  calculations  of 
Tougard  to  the  effect  that  by  agamic  multiplication  "  a  single 
impregnated  ovum  of  Aphis  may  give  rise,  without  fecundation, 
to  a  quintillion  of  Aphides,"  Professor  Huxley  says  : — 

"  I  will  assume  that  an  Aphis  weighs  -rihtv  of  a  grain,  which  is  certainly 
vastly  under  the  mark.  A  quintillion  of  Aphides  will,  on  this  estimate, 
weigh  a  quatrillion  of  grains.  He  is  a  very  stout  man  who  weighs  two  million 
grains;  consequently  the  tenth  brood  alone,  if  all  its  members  survive 
the  perils  to  which  they  are  exposed,  contains  more  substance  than  600,- 
000,000  stout  men— to  say  the  least,  more  than  the  whole  population  of 
China!"* 

And  had  Professor  Huxley  taken  the  actual  weight,  one-twelfth 
of  a  grain,  the  quintillion  of  Aphides  would  evidently  far  out- 
weigh the  whole  human  population  of  the  globe  :  five  billions  of 
tons  being  the  weight,  as  brought  out  by  my  own  calculation !  Of 

*  Tfie  Transactions  of  the  Linncean  Society  of  London,  Vol.  XXII,  p.  215. 
The  estimate  of  Reaumur,  cited  by  Kirby  and  Spence,  is  still  higher — "in  five 
generations  one  Aphis  may  be  the  progenitor  of  5,904,900,00tf  descendants  ; 
and  that  it  is  supposed  that  in  one  year  there  may  be  twenty  generations," 
(Introduction  to  Entomology,  Vol.  I,  p.  175) 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.       041 

course  I  do  not  cite  this  in  proof  of  the  extent  to  which  multipli- 
cation of  somatic  cells,  descending  from  a  single  ovum,  may  go ; 
because  it  will  be  contended,  with  some  reason,  that  each  of  the 
sexless  Aphides,  viviparously  produced,  arose  by  fission  of  a  cell 
which  had  descended  from  the  original  reproductive  cell.  I  cite 
it  merely  to  show  that  when  the  cell-products  of  a  fertilized 
ovum  are  perpetually  divided  and  subdivided  into  small  groups, 
distributed  over  an  unlimited  nutritive  area,  so  that  they  can 
get  materials  for  growth  at  no  cost,  and  expend  nothing  appre- 
ciable in  motion  or  maintenance  of  temperature,  cell-production 
may  go  on  without  limit.  For  the  agamic  multiplication  of 
Aphides  has  been  shown  to  continue  for  four  years,  and  to  all 
appearance  would  be  ceaseless  were  the  temperature  and  supply 
of  food  continued  without  break.  But  now  let  us  pass  to  analo- 
gous illustrations  of  cause  and  consequence,  open  to  no  criticism 
of  the  kind  just  indicated.  They  are  furnished  by  various  kinds 
of  Entozoa,  of  which  take  the  Trematoda,  infesting  molluscs  and 
fishes.  Of  one  of  them  we  read  : — "  Gyrodactylus  multiplies 
agamicaliy  by  the  development  of  a  young  Trematode  within 
the  body,  as  a  sort  of  internal  bud.  A  second  generation  appears 
within  the  first,  and  even  a  third  within  the  second,  before  the 
young  Gyrodactylus  is  born."  *  And  the  drawings  of  Steenstrup, 
in  his  Alternation  of  Generations,  show  us,  among  creatures  of  this 
group,  a  sexless  individual  the  whole  interior  of  which  is  trans- 
formed into  smaller  sexless  individuals,  which  severally,  before  or 
after  their  emergence,  undergo  similar  transformations — a  multi- 
plication of  somatic  cells  without  any  sign  of  reproductive  cells. 
Under  what  circumstances  do  such  modes  of  agamic  multiplica- 
tion, variously  modified  among  parasites,  occur  ?  They  occur 
where  there  is  no  expenditure  whatever  in  motion  or  maintenance 
of  temperature,  and  where  nutriment  surrounds  the  body  on  all 
sides.  Other  instances  are  furnished  by  groups  in  which,  though 
the  nutriment  is  not  abundant,  the  cost  of  living  is  almost  un- 
appreciable.  Among  the  Coelenterata  there  are  the  Hydroid 
Polyps,  simple  and  compound  ;  and  among  the  Mollusca  we  have 
various  types  of  Ascidians,  fixed  and  floating,  Botryllidce  and 
Sal  pee. 

But  now  from  these  low  animals  in  which  sexless  reproduction, 
and  continued  multiplication  of  somatic  cells,  is  common,  and 
one  class  of  which  is  named  "  zoophytes,"  because  its  form  of 
life  simulates  that  of  plants,  let  us  pass  to  plants  themselves.  In 
these  there  is  no  expenditure  in  effort,  there  is  no  expenditure  in 
maintaining  temperature,  and  the  food,  some  of  it  supplied  bv 
the  earth,  is  the  rest  of  it  supplied  by  a  medium  which  every- 

*  A  Manual  of  tJie  Anatomy  of  Invertelra'.ed  Animals,  by  T.  H.  Huxley, 
P.  206. 


(U2  APPENDIX  B. 

where  bathes  the  outer  surface  :  the  utilization  of  its  contained 
material  being  effected  gratis  by  the  Sun's  rays.  Just  as  was  to 
be  expected,  we  here  find  that  agamogenesis  may  go  on  without 
end.  Numerous  plants  and  trees  are  propagated  to  an  unlimited 
extent  by  cuttings  and  buds  ;  and  we  have  sundry  plants  which 
cannot  be  otherwise  propagated.  The  most  familiar  are  the 
double  roses  of  our  gardens  :  these  do  not  seed,  and  yet  have 
been  distributed  everywhere  by  grafts  and  buds.  Hothouses 
furnish  many  cases,  as  I  learn  from  an  authority  second  to  none. 
Of  "  the  whole  host  of  tropical  orchids,  for  instance,  not  one  per 
cent,  has  ever  seeded,  and  some  have  been  a  century  under  culti- 
vation." Again,  we  have  the  Acorus  calamus,  "  that  has  hardly 
been  known  to  seed  anywhere,  though  it  is  found  wild  all  over 
the  north  temperate  hemisphere."  And  then  there  is  the  con- 
spicuous and  conclusive  case  of  Eloidea  Canadensis  (alias  An- 
acharis,)  introduced  no  one  knows  how  (probably  with  timber), 
and  first  observed  in  1847,  in- several  places;  and  which,  having 
since  spread  over  nearly  all  England,  now  everywhere  infests 
ponds,  canals,  and  slow  rivers.  The  plant  is  dio?cious,  and  only 
the  female  exists  here.  Beyond  all  question,  therefore,  this  vast 
progeny  of  the  first  slip  or  fragment  introduced,  sufficient  to 
cover  many  square  miles  were  it  put  together,  is  constituted 
entirely  of  somatic  cells.  Hence,  as  far  as  we  can  judge,  these 
somatic  cells  are  immortal  in  the  sense  given  to  the  word  by 
Professor  Weismann ;  and  the  evidence  that  they  are  so  is  im- 
measurably stronger  than  the  evidence  which  leads  him  to  assert 
immortality  for  the  fissiparously-multiplying  Protozoa.  This 
endless  multiplication  of  somatic  cells  has  been  going  on  under 
the  eyes  of  numerous  observers  for  forty  odd  years.  What 
observer  has  watched  for  forty  years  to  see  whether  the  fissi- 
parous  multiplication  of  Protozoa  does  not  cease  ?  What  ob- 
server has  watched  for  one  year,  or  one  month,  or  one  week  ?  * 

Even  were  not  Professor  Weismann's  theory  disposed  of  by 
this  evidence,  it  might  be  disposed  of  by  a  critical  examination 
of  his  own  evidence,  using  his  own  tests.  Clearly,  if  we  are  to 

*  Respecting  the  Elmdei  I  learn  that  in  1879— thirty  years  after  it  had 
become  a  pest — one  solitary  male  plant  was  found  in  a  pond  near  Edin- 
burgh ;  but  "  in  an  exhaustive  inquiry  on  the  plant  made  by  Dr.  Greenland, 
of  Copenhagen,  he  could  find  no  trace  of  any  male  specimens  having  been 
found  in  Europe  other  than  the  Scotch."  In  waters  from  which  the 
Eloidea  has  disappeared,  it  seems  to  have  done  so  in  consequence  of  the 
growth  of  an  Alga,  which  has  produced  turbid  water  unfavourable  to  it. 
That  is  to  say,  the  decreased  multiplication  of  somatic  cells  in  some  cases, 
is  not  due  to  any  exhaustion,  but  is  caused  by  the  rise  of  enemies  or 
adverse  conditions;  as  happens  generally  with  introduced  species  of  plants 
and  animals  which  multiply  at  first  enormously,  and  then,  without  any  loss  of 
reproductive  power,  begin  to  decrease  under  the  antagonizing  influences  which 
grow  up. 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      C43 

measure  relative  mortalities,  we  must  assume  the  conditions  to  be 
the  same  and  must  use  the  same  measure.  Let  us  do  this  with 
some  appropriate  animal — say  Man,  as  the  most  open  to  observa- 
tion. The  mortality  of  the  somatic  cells  constituting  the  mass  of 
the  human  body,  is,  according  to  Professor  Weismann,  shown  by 
the  decline  and  final  cessation  of  cell-multiplication  in  its  various 
organs.  Suppose  we  apply  this  test  to  all  the  organs:  not  to 
those  only  in  which  there  continually  arise  bile-cells,  epithelium- 
cells,  &c.,  but  to  those  also  in  which  there  arise  reproductive 
cells.  What  do  we  find  ?  That  the  multiplication  of  these  last 
comes  to  an  end  long  before  the  multiplication  of  the  first.  In 
a  healthy  woman,  the  cells  which  constitute  the  various  active  tis- 
sues of  the  bod^T,  continue  to  grow  and  multiply  for  many  years 
after  germ-cells  have  died  out.  If  similarly  measured,  then,  these 
cells  of  the  last  class  prove  to  be  more  mortal  than  those  of  the 
first.  But  Professor  Weismann  uses  a  different  measure  for  the 
two  classes  of  cells.  Passing  over  the  illegitimacy  of  this  pro- 
ceeding, let  us  accept  his  other  mode  of  measurement,  and  see 
what  comes  of  it.  As  described  by  him,  absence  of  death  among 
the  Protozoa  is  implied  by  that  unceasing  division  and  subdivision 
of  which  they  are  said  to  be  capable.  Fission  continued  without 
end,  is  the  definition  of  the  immortality  he  speaks  of.  Apply 
this  conception  to  the  reproductive  cells  in  a  Metazoon.  That  the 
immense  majority  of  them  do  not  multiply  without  end,  we  have 
already  seen :  with  very  rare  exceptions  they  die  and  disappear 
without  result,  and  they  cease  their  multiplication  while  the  body 
as  a  whole  still  lives.  But  what  of  those  extremely  exceptional 
ones  which,  as  being  actually  instrumental  to  the  maintenance 
of  the  species,  are  alone  contemplated  by  Professor  Weismann  ? 
Do  these  continue  their  fissiparous  multiplications  without  end  ? 
By  no  means.  The  condition  under  which  alone  they  preserve  a 
qualified  form  of  existence,  is  that,  instead  of  one  becoming  two, 
two  become  one.  A  member  of  series  A  and  a  member  of  series  B, 
coalesce ;  and  so  lose  their  individualities.  Now,  obviously,  if  the 
immortality  of  a  series  is  shown  if  its  members  divide  and  sub- 
divide perpetually,  then  the  opposite  of  immortality  is  shown 
when,  instead  of  division,  there  is  union.  Each  series  ends,  and 
there  is  initiated  a  new  series,  differing  more  or  less  from  both. 
Thus  the  assertion  that  the  reproductive  cells  are  immortal,  can  be 
defended  only  by  changing  the  conception  of  immortality  other- 
wise implied. 

Even  apart  from  these  last  criticisms,  however,  we  have  clear 
disproof  of  the  alleged  inherent  difference  between  the  two  classes 
of  cells.  Among  animals,  the  multiplication  of  somatic  cells  is 
brought  to  an  end  by  sundry  restraining  conditions ;  but  in  varior.s 
plants,  where  these  restraining  conditions  are  absent,  the  multi- 


644:  APPENDIX   B. 

plication  is  unlimited.  *  It  may,  indeed,  be  said  tliat  the  alleged 
distinction  should  be  reversed  ;  since  the  fissiparous  multiplication 
of  reproductive  cells  is  necessarily  interrupted  from  time  to  time 
by  coalescence,  while  that  of  the  somatic  cells  may  go  on  for  a 
century  without  being  interrupted. 

In  the  essay  to  which  this  is  a  postscript,  conclusions  were 
drawn  from  the  remarkable  case  of  the  horse  and  the  quagga, 
there  narrated,  along  with  an  analogous  case  observed  among 
pigs.  These  conclusions  have  since  been  confirmed.  I  am  much 
indebted  to  a  distinguished  correspondent  who  has  drawn  my 
attention  to  verifying  facts  furnished  by  the  offspring  of  whites 
and  negroes  in  the  United  States.  Referring  to  information  given 
him  many  years  ago,  he  says: — "It  was  to  the  effect  that  the 
children  of  white  women  by  a  white  father,  had  been  repeatedly 
observed  to  show  traces  of  black  blood,  in  cases  when  the  woman 
had  previous  connection  with  [i.e.  a  child  by]  a  negro."  At  the 
time  I  received  this  information,  an  American  was  visiting  'me ; 
and,  on  being  appealed  to,  answered  that  in  the  United  States 
there  was  an  established  belief  to  this  effect.  Not  wishing,  how- 
ever, to  depend  upon  hearsay,  I  at  once  wrote  to  America  to 
make  inquiries.  Professor  Cope  of  Philadelphia  has  written  to 
friends  in  the  South,  but  has  not  yet  sent  me  the  results.  Pro- 
fessor Marsh,  the  distinguished  palaeontologist,  of  Yale,  New 
Haven,  who  is  also  collecting  evidence,  sends  a  preliminary  letter 
in  which  he  says : — "  I  do  not  myself  know  of  such  a  case,  but 
have  heard  many  statements  that  make  their  existence  probable. 
One  instance,  in  Connecticut,  is  vouched  for  so  strongly  by  an 
acquaintance  of  mine,  that  I  have  good  reason  to  believe  it  to 
be  authentic." 

That  cases  of  the  kind  should  not  be  frequently  seen  in  the 
North,  especially  nowadays,  is  of  course  to  be  expected.  The 
first  of  the  above  quotations  refers  to  facts  observed  in  the  South 
during  slavery  days ;  and  even  then,  the  implied  conditions  were 
naturally  very  infrequent.  Dr.  W.  J.  Youmans  of  New  York  has, 
on  my  behalf,  interviewed  several  medical  professors,  who,  though 
they  have  not  themselves  met  with  instances,  say  that  the  alleged 
result,  described  above,  "  is  generally  accepted  as  a  fact."  But 
he  gives  me  what  I  think  must  be  regarded  as  authoritative  tes- 
timony. It  is  a  quotation  from  the  standard  work  of  Professor 
Austin  Flint,  and  runs  as  follows: — 

"A  peculiar  and,  it  seems  to  me,  an  inexplicable  fact  is,  that  previous 
pregnancies  have  an  influence  upon  offspring.  This  is  well  known  to  breeders 
of  animals.  If  pure-blooded  mares  or  bitches  have  been  once  covered  by  an 
inferior  male,  in  subsequent  fecundations  the  young  are  likely  to  partake  of 
the  character  of  the  first  male,  even  if  they  be  afterwards  bred  with  males  of 
unimpeachable  pedigree.  What  the  mechanism  of  the  influence  of  "the  first 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.       045 

conception  is,  it  is  impossible  to  say;  but  the  fact  is  incontestable.  The  san  c 
influence  is  observed  in  the  human  subject.  A  woman  may  have,  by  a  second 
husband,  children  who  resemble  a  former  husband,  and  this  is  particularly 
well  marked  in  certain  instances  by  the  colour  of  the  hair  and  eyes.  A  white 
woman  who  has  had  children  by  a  negro  may  subsequently  bear  children  to  a 
white  man,  these  child.en  presenting  some  of  the  unmistakable  peculiarities 
of  the  negro  raco."  " 

Dr.  Youmans  called  on  Professor  Flint,  who  remembered  "  investi- 
gating the  subject  at  the  time  his  larger  work  was  written  [the 
above  is  from  an  abridgment],  and  said  that  he  had  never  heard 
the  statement  questioned." 

Some  days  before  I  received  this  letter  and  its  contained  quo- 
tation, the  remembrance  of  a  remark  I  heard  many  years  ago  con- 
cerning dogs,  led  to  the  inquiry  whether  they  furnished  analogous 
evidence.  It  occurred  to  me  that  a  friend  who  is  frequently 
appointed  judge  of  animals  at  agricultural  shows,  Mr.  Fookes, 
of  Fair-field,  Pewsey,  Wiltshire,  might  know  something  about  the 
matter.  A  letter  to  him  brought  various  confirmatory  state- 
ments. From  one  "who  had  bred  dogs  for  many  years"  he 
learnt  that — 

"  It  is  a  well  known  and  admitted  fact  that  if  a  bitch  has  two  litters  by 
two  different  dogs,  the  character  of  the  first  father  is  sure  to  be  perpetuated 
in  any  litters  she  may  afterwards  have,  no  matter  how  pure-bred  a  dog  may 
be  the  begetter." 

After  citing  this  testimony,  Mr.  Fookes  goes  on  to  give  illus- 
trations known  to  himself. 

"  A  friend  of  mine  near  this  had  a  very  valuable  Dachshund  bitch,  which 
most  unfortunately  had  a  litter  by  a  stray  sheep-dog.  The  next  year  her 
owner  sent  her  on  a  visit  to  a  pure  Dachshund  dog,  but  the  produce  took  quite 
as  much  of  the  first  father  as  the  second,  and  the  next  year  he  sent  her  to 
another  Dachshund  with  the  same  result.  Another  case : — A  friend  of  mine 
in  Devizes  had  a  litter  of  puppies,  unsought  for,  by  a  setter  from  a  favourite 
pointer  bitch,  and  after  this  she  never  bred  any  true  pointers,  no  matter  of 
what  the  paternity  was." 

[Since  the  publication  of  this  article  additional  evidences  have  com*  to 
hand.  One  is  from  the  late  Prof.  Rilcy,  State  Entomologist  at  Washington, 
who  says  that  tclegony  is  an  "established  principle  among  well-educated 
farmers  "  in  the  United  States,  and  who  gives  me  a  case  in  horse-breeding  to 
which  he  was  himself  witness. 

Mr.  W.  P.  Smith,  writing  from  Stoughton  Grange,  Guildford,  but  giving 
the  results  of  his  experiences  in  America,  says  that  "  the  fact  of  a  previous 
conception  influencing  subsequent  offspring  was  so  far  recognised  among 
American  cattle-breeders "  that  it  was  proposed  to  raise  the  rank  of  any 
heifer  that  had  borne  a  first  calf  by  a  thoroughbred  bull,  and  though  this 
resolution  when  brought  before  one  of  the  chief  societies  was  not  carried, 
yet  on  all  sides  it  was  admitted  that  previous  conceptions  had  effects  of 
the  kind  alleged.  Mr.  Smith  in  another  letter  says:— "When  I  had  a 
large  mule  and  horse  ranche  in  America  I  noticed  that  the  foals  of  mares 

*  A    Text  Book  of  Human  Physiology.     By  Austin  Flint,   M.D.,  LL.D. 
Fourth  edition.     New  York:  D.  Ap'pleton  &  Co.  1888.     Page  797. 
42 


646  APPENDIX  B. 

by  horse  stallions  had  a  mulish  appearance  in  those  cases  where  the  mare  had 
previously  given  birth  to  a  mule  foal.  Common  heifers  who  have  had  calves 
by  a  thoroughbred  bull  are  apt  thereafter  to  have  well-bred  calves  even  from 
the  veriest  scrubs." 

Yet  another  very  interesting  piece  of  evidence  is  furnished  by  Mr.  W. 
Scdgwick,  M.R.C.S.,  in  an  article  on  "The  Influence  of  Heredity  in 
Disease,"  published  in  the  British  Medical  Journal  for  Feb.  22,  1896,  pp. 
460-2.  It  concerns  the  transmission  of  a  malformation  known  among 
medical  men  as  hypospadias.  Referring  to  a  man  belonging  to  a  family  in 
which  this  defect  prevailed,  he  writes : — "  The  widow  of  the  man  from  whom 
these  three  generations  of  hypospadians  were  descended  married  again,  after 
an  interval  of  eighteen  months ;  and  in  this  instance  the  second  husband  was 
not  only  free  from  the  defect,  but  there  was  no  history  of  it  in  his  family. 
By  this  second  marriage  she  had  four  hypospadiac  sons  and  four  hypospadiac 
grandsons ;  whilst  there  were  seven  grandsons  and  three  great-grandsons  who 
were  not  mal-formed."] 

Coming  from  remote  places,  from  those  who  have  no  theory 
to  support,  and  who  are  some  of  them  astonished  by  the  unex- 
pected phenomena,  the  agreement  dissipates  all  doubt.  In  four 
kinds  of  mammals,  widely  divergent  in  their  natures — man,  horse, 
dog,  and  pig — we  have  this  same  seemingly-anomalous  kind  of 
heredity,  made  visible  under  analogous  conditions.  We  must  take 
it  as  a  demonstrated  fact  that,  during  gestation,  traits  of  constitution 
inherited  from  the  father  produce  effects  upon  the  constitution  of 
the  mother ;  and  that  these  communicated  effects  are  transmitted 
by  her  to  subsequent  offspring.  We  are  supplied  with  an  abso- 
lute disproof  of  Professor  Weismann's  doctrine  that  the  repro- 
ductive cells  are  independent  of,  and  uninfluenced  by,  the  somatic 
cells ;  and  there  disappears  absolutely  the  alleged  obstacle  to  the 
transmission  of  acquired  characters. 

Notwithstanding  experiences  showing  the  futility  of  contro- 
versy for  the  establishment  of  truth,  I  am  tempted  here  to  answer 
opponents  at  some  length.  But  even  could  the  editor  allow  me 
the  needful  space,  I  should  be  compelled,  both  by  lack  of  time 
and  by  ill-health,  to  be  brief.  I  must  content  myself  with  notic- 
ing a  few  points  which  most  nearly  concern  me. 

Referring  to  my  argument  respecting  tactual  discriminative- 
ness,  Mr.  Wallace  thinks  that  I — 

"  afford  a  glaring  example  of  taking  the  unessential  in  place  of  the  essential, 
and  drawing  conclusions  from  a  partial  and  altogether  insufficient  survey  of 
the  phenomena.  For  this  'tactual  discriminativeness,'  which  is  alone  dealt 
with  by  Mr.  Spencer,  forms  the  least  important,  and  probably  only  an  inci- 
dental portion  of  the  great  vital  phenomenon  of  skin-sensitiveness,  which  is  at 
once  the  watchman  and  the  shield  of  the  organism  against  imminent  external 
dangers."  (Fortnightly  Review,  April,  1893,  p.  497) 

Here  Mr.  Wallace  assumes  it  to  be  self-evident  that  skin-sensi- 
tiveness is  due  to  natural  selection,  and  assumes  that  this  must  be 
admitted  by  me.  lie  supposes  it  is  only  the  unequal  distribution 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      (U7 

of  skin-discriminativeness  which  I  contend  is  not  thus  accounted 
for.  But  I  deny  that  either  the  general  sensitiveness  or  the 
special  sensitiveness  results  from  natural  selection  ;  and  I  have 
years  ago  justified  the  first  disbelief  as  I  have  recently  the  second. 
In  "The  Factors  of  Organic  Evolution"  (Essays,  454—8),  I 
have  given  various  reasons  for  inferring  that  the  genesis  of  the 
nervous  system  cannot  be  due  to  survival  of  the  fittest ;  but  that 
it  is  due  to  the  direct  effects  of  converse  between  the  surface  and 
the  environment ;  and  that  thus  only  is  to  be  explained  the 
strange  fact  that  the  nervous  centres  are  originallv  superficial,  and 
migrate  inwards  during  development.  These  conclusions  I  have, 
in  the  essay  Mr.  Wallace  criticizes,  upheld  by  the  evidence  which 
blind  boys  and  skilled  compositors  furnish  ;  proving,  as  this  does, 
that  increased  nervous  development  is  peripherally  initiated.  Mr. 
Wallace's  belief  that  skin-sensitiveness  arose  by  natural  selection, 
is  unsupported  by  a  single  fact.  He  assumes  that  it  must  have 
been  so  produced  because  it  is  all-important  to  self-preservation. 
My  belief  that  it  is  directly  initiated  by  converse  with  the  environ- 
ment, is  supported  by  facts  ;  and  I  have  given  proof  that  the 
assigned  cause  is  now  in  operation.  Am  I  called  upon  to  abandon 
my  own  supported  belief  and  accept  Mr.  Wallace's  unsupported 
belief  ?  I  think  not. 

Referring  to  my  argument  concerning  blind  cave-animals, 
Professor  Lankester,  in  Nature  of  February  23,  1893,  writes: — 

"  Mr.  Spencer  shows  that  the  saving  of  ponderable  material  in  the  sup- 
pression of  an  eye  is  but  a  small  economy :  he  loses  sight  of  the  fact,  however, 
that  possibly,  or  even  probably,  the  saving  to  the  organism  in  the  reduction 
of  an  eye  to  a  rudimentary  state  is  not  to  be  measured  by  mere  bulk,  but  by 
the  non-expenditure  of  special  materials  and  special  activities  which  are  con- 
cerned in  the  production  of  an  organ  so  peculiar  and  elaborate  as  is  the  verte- 
brate eye.'' 

It  seems  to  me  that  a  supposition  is  here  made  to  do  duty  as  a 
fact ;  and  that  I  might  with  equal  propriety  say  that  "  possibly, 
or  even  probably,"  the  vertebrate  eye  is  physiologically  cheap  : 
its  optical  part,  constituting  nearly  its  whole  bulk,  consisting  of 
a  low  order  of  tissue.  There  is,  indeed,  strong  reason  for  con- 
sidering it  physiologically  cheap.  If  any  one  remembers  how 
relatively  enormous  are  the  eyes  of  a  fish  just  out  of  the  egg — a 
pair  of  eyes  with  a  body  and  head  attached  ;  and  if  he  then 
remembers  that  every  egg  contains  material  for  such  a  pair  of 
eyes  ;  he  will  see  that  eye-material  constitutes  a  very  considerable 
part  of  the  fish's  roe  ;  and  that,  since  the  female  fish  provides 
this  quantity  every  year,  it  cannot  be  expensive.  My  argument 
against  Weismann  is  strengthened  rather  than  weakened  by  con- 
templation of  these  facts. 

Professor  Lankester  asks  my  attention  to  a  hypothesis  of  his 


048  APPENDIX  B. 

own,  published  in  the  Encyclopaedia  Britannica,  concerning  the 
production  of  blind  cave-animals.  He  thinks  it  can — 

"  be  fully  explained  by  natural  selection  acting  on  congenital  fortuitous  varia- 
tions. Many  animals  are  thus  born  with  distorted  or  defective  eyes  who.<e 
parents  have  not  had  their  eyes  submitted  to  any  peculiar  conditions.  Sup- 
posing a  number  of  some  species  of  Arthropod  or  Fish  to  be  swept  into  a 
cavern  or  to  be  carried  from  less  to  greater  depths  in  the  sea,  those  individu- 
als with  perfect  eyes  would  follow  the  glimmer  of  light  and  eventually  escape 
to  the  outer  air  or  the  shallower  depths,  leaving  behind  those  with  imperfect 
eyes  to  breed  in  the  dark  place.  A  natural  selection  would  thus  be  effected  " 
in  successive  generations. 

First  of  all,  I  demur  to  the  words  "  many  animals."  Under  the 
abnormal  conditions  of  domestication,  congenitally  defective  eyes 
may  be  not  very  uncommon  ;  but  their  occurrence  under  natural 
conditions  is,  I  fancy,  extremely  rare.  Supposing,  however,  that 
in  a  shoal  of  young  fish,  there  occur  some  with  eyes  seriously 
defective.  What  will  happen  ?  Vision  is  all-important  to  the 
young  fish,  both  for  obtaining  food  and  for  escaping  from  enemies. 
This  is  implied  by  the  immense  development  of  eyes  just  referred 
to  ;  and  the  obvious  conclusion  to  be  drawn  is  that  the  partially 
blind  would  disappear.  Considering  that  out  of  the  enormous 
number  of  young  fish  hatched  with  perfect  eyes,  not  one  in  a 
hundred  reaches  maturity,  what  chance  of  surviving  would  there 
be  for  those  with  imperfect  eyes  ?  Inevitably  they  would  be 
starved  or  be  snapped  up.  Hence  the  chances  that  a  matured  or 
partially  matured  semi-blind  fish,  or  rather  two  such,  male  and 
female,  would  be  swept  into  a  cave  and  left  behind  are  extremely 
remote.  Still  more  remote  must  the  chances  be  in  the  case  of 
cray-fish.  Sheltering  themselves  as  these  do  under  stones,  in 
crevices,  and  in  burrows  which  they  make  in  the  banks,  and  able 
quickly  to  anchor  themselves  to  weeds  or  sticks  by  their  claws,  it 
seems  scarcely  supposable  that  any  of  them  could  be  carried  into 
a  cave  by  a  flood.  What,  then,  is  the  probability  that  there  will 
be  two  nearly  blind  ones,  and  that  these  will  be  thus  carried  ? 
Then,  after  this  first  extreme  improbability,  there  comes  a  second, 
which  we  may,  I  think,  rather  call  an  impossibility.  Plow  would 
it  be  possible  for  creatures  subject  to  so  violent  a  change  of 
habitat  to  survive  ?  Surely  death  would  quickly  follow  the  sub- 
jection to  such  utterly  unlike  conditions  and  modes  of  life.  The 
existence  of  these  blind  cave-animals  can  be  accounted  for  only 
by  supposing  that  their  remote  ancestors  began  making  excursions 
into  the  cave,  and,  finding  it  profitable,  extended  them,  genera- 
tion after  generation,  further  in  :  undergoing  the  required  adapta- 
tions little  by  little.* 

*  Thia  supposition  I  find  verified  by  Mr.  A.  S.  Packard  in  his  elaborate 
monograph  on  "  The  Cave  Fauna  of  North  America,  &c.,"  as  also  in  his  article 
published  in  the  American  Naturalist,  September,  1883;  for  he  there  men- 


INADEQUACY  OP  NATURAL  SELECTION,   ETC.      tf49 

Between  Dr.  Romanes  and  myself  the  first  difference  concerns 
the  interpretation  of  "  Panmixia."  Clearer  conceptions  of  these 
matters  would  be  reached  if,  instead  of  thinking  in  abstract  terms, 
the  physiological  processes  concerned  were  brought  into  the  fore- 
ground. Beyond  the  production  of  changes  in  the  sizes  of  parts 
by  the  selection  of  fortuitously-arising  variations,  I  can  see  but 
one  other  cause  for  the  production  of  them — the  competition 
among  the  parts  for  nutriment.  This  has  the  effect  that  active 
parts  are  well-supplied  and  grow,  while  inactive  parts  are  ill- 
supplied  and  dwindle.*  This  competition  is  the  cause  of 
"  economv  of  growth"  ;  this  is  the  cause  of  decrease  from  disuse ; 
and  this  is  the  only  conceivable  cause  of  that  decrease  which  Dr. 
Romanes  contends  follows  the  cessation  of  selection.  The  three 
things  are  aspects  of  the  same  thing.  And  now,  before  leaving 
this  question,  let  me  remark  on  the  strange  proposition  which 
has  to  be  defended  by  those  who  deny  the  dwindling  of  organs 
from  disuse.  Their  proposition  amounts  to  this  : — that  for  a 
hundred  generations  an  inactive  organ  may  be  partially  denuded 
of  blood  all  through  life,  and  yet  in  the  hundredth  generation 
will  be  produced  of  just  the  same  size  as  in  the  first ! 

There  is  one  other  passage  in  Dr.  Romanes'  criticism — that 
concerning  the  influence  of  a  previous  sire  on  progeny — which 
calls  for  comment.  He  sets  down  what  he  supposes  Weismann 
will  say  in  response  to  my  argument.  "  First,  he  may  question 
the  fact."  Well,  after  the  additional  evidence  given  above,  I 
think  he  is  not  likely  to  do  that ;  unless,  indeed,  it  be  that  along 
with  readiness  to  base  conclusions  on  things  "  it  is  easy  to 
imagine  "  there  goes  reluctance  to  accept  testimony  which  it  is 
difficult  to  doubt.  Second,  he  is  supposed  to  reply  that  "  the 
Germ-plasm  of  the  first  sire  has  in  some  way  or  another  become 
partly  commingled  with  that  of  the  immature  ova " ;  and  Dr. 
Romanes  goes  on  to  describe  how  there  may  be  millions  of 
spermatozoa  and  "  thousands  of  millions "  of  their  contained 
"  ids  "  around  the  ovaries,  to  which  these  secondary  effects  are 

tions  "variations  in  Pseudotremia  cavernarum  and  Tomocerus  plumbeus, 
found  living  near  the  entrance  to  caves  in  partial  daylight."  The  facts,  as 
accumulated  by  Mr.  Packard,  furnished  a  much  more  complete  answer  to 
Prof.  Lankester  than  is  above  given,  as,  for  example,  the  "blindness  of 
Ntotoma,  or  the  Wood-Rat  of  Mammoth  Cave."  It  seems  that  there  are  also 
"  cave  beetles,  with  or  without  rudimentary  eyes,"  and  "  eyeless  spiders  "  and 
Mvriapods.  And  there  are  insects,  as  some  "species  of  Anophthalmus  and 
Adelops,  whose  larvae  are  lacking  in  all  traces  of  eyes  and  optic  nerves  and 
lobes."  These  instances  cannot  be  explained  as  sequences  of  an  inrush  of 
wnter  carrying  with  it  the  remote  ancestors,  some  of  which  did  not  find  their 
way  out ;  nor  can  others  of  them  be  explained  by  supposing  an  inrush  of  ai-, 
which  did  the  like. 

*  See  "Social  Organism  "  in  Westminster  Review  for  January,  I860;  aLo 
Principles  of  Sociology,  §  247. 


650  APPENDIX  B. 

due.  But,  on  the  one  hand,  he  does  not  explain  why  in  such 
cases  each  subsequent  ovum,  as  it  becomes  matured,  is  not  fer- 
tilized by  the  sperm-cells  present,  or  their  contained  germ-plasm, 
rendering  all  subsequent  fecundations  needless  ;  and,  on  the  other 
hand,  he  does  not  explain  why,  if  this  does  not  happen,  the 
potency  of  this  remaining  germ-plasm  is  nevertheless  such  as  to 
affect  not  only  the  next  succeeding  offspring,  but  all  subsequent 
offspring.  The  irreconcilability  of  these  two  implications  would,  I 
think,  sufficiently  dispose  of  the  supposition,  even  had  we  not  daily 
multitudinous  proofs  that  the  surface  of  a  mammalian  ovarium  is 
not  a  spermatheca.  The  third  reply  Dr.  Romanes  urges,  is  the 
inconceivability  of  the  process  by  which  the  germ-plasm  of  a  pre- 
ceding male  parent  affects  the  constitution  of  the  female  and  her 
subsequent  offspring.  In  response,  I  have  to  ask  why  he  piles 
up  a  mountain  of  difficulties  based  on  the  assumption  that  Mr. 
Darwin's  explanation  of  heredity  by  "  Pangenesis  "  is  the  only 
available  explanation  preceding  that  of  Wcismann  ?  and  why 
he  presents  these  difficulties  to  me,  more  especially  ;  deliberately 
ignoring  my  own  hypothesis  of  physiological  units  ?  It  cannot 
be  that  he  is  ignorant  of  this  hypothesis,  since  the  work  in  which 
it  is  variously  set  forth  (Principles  of  Biology,  §§  66 — 97)  is  one 
with  which  he  is  well  acquainted  :  witness  his  Scientific  Evidences 
of  Organic  Evolution  ;  and  he  has  had  recent  reminders  of  it  in 
Weismann's  Germ-plasm,  where  it  is  repeatedly  referred  to.  Why, 
then,  does  he  assume  that  I  abandon  my  own  hypothesis  and 
adopt  that  of  Darwin ;  thereby  entangling  myself  in  difficulties 
which  my  own  hypothesis  avoids  ?  If,  as  I  have  argued,  the 
germ-plasm  consists  of  substantially  similar  units  (having  only 
those  minute  differences  expressive  of  individual  and  ancestral 
differences  of  structure),  none  of  the  complicated  requirements 
which  Dr.  Romanes  emphasizes  exist ;  and  the  alleged  incon- 
ceivability disappears. 

Here  I  must  end :  not  intending  to  say  more,  unless  for  some 
very  urgent  reason ;  and  leaving  others  to  carry  on  the  discus- 
sion. I  have,  indeed,  been  led  to  suspend  for  a  short  time  my 
proper  work,  only  by  consciousness  of  the  transcendent  import- 
ance of  the  question  at  issue.  As  I  have  before  contended,  a 
right  answer  to  the  question  whether  acquired  characters  are  or 
are  not  inherited,  underlies  right  beliefs,  not  only  in  Biology  and 
Psychology,  but  also  in  Education,  Ethics,  and  Politics. 


III. 

As  a  species  of  literature,  controversy  is  characterised  bv  a 
terrible  fertility.     Each  proposition  becomes  the  parent  of  half  a 


INADEQUACY  OP  NATURAL  SELECTION,   ETC.       651 

dozen ;  so  that  a  few  replies  and  rejoinders  produce  an  un- 
manageable population  of  issues,  old  and  new,  which  end  in 
being  a  nuisance  to  everybody.  Remembering  this,  I  shall  re- 
frain from  dealing  with  all  the  points  of  Professor  Weismann's 
answer.  I  must  limit  myself  to  a  part ;  and  that  there  may  be 
no  suspicion  of  a  selection  convenient  to  myself,  I  will  take  those 
contained  in  his  first  article. 

Before  dealing  with  his  special  arguments,  let  me  say  some- 
thing about  the  general  mode  of  argument  which  Professor  Weis- 
mann  adopts. 

The  title  of  his  article  is  "The  All-Sufficiency  of  Natural 
Selection."  *  Very  soon,  however,  as  on  p.  322,  we  come  to  the 
admission,  which  he  has  himself  italicised,  "  that  it  is  really  very 
difficult  to  imagine  this  process  of  natural  selection  in  its  details;  and 
to  this  day  it  is  impossible  to  demonstrate  it  in  any  one  point." 
Elsewhere,  as  on  pp.  327  and  336  a  propos  of  other  cases,  there 
are  like  admissions.  But  now  if  the  sufficiency  of  an  assigned 
cause  cannot  in  any  case  be  demonstrated,  and  if  it  is  "  really 
very  difficult  to  imagine "  in  what  way  it  has  produced  its  al- 
leged effects,  what  becomes  of  the  "all-sufficiency"  of  the  cause  ? 
How  can  its  all-sufficiency  be  alleged  when  its  action  can  neither 
be  demonstrated  nor  easily  imagined  ?  Evidently  to  fit  Professor 
Weismann's  argument  the  title  of  the  article  should  have  been 
"  The  Doubtful  Sufficiency  of  Natural  Selection." 

Observe,  again,  how  entirely  opposite  are  the  ways  in  which 
he  treats  his  own  interpretation  and  the  antagonist  interpreta- 
tion. He  takes  the  problem  presented  by  certain  beautifully 
adapted  structures  on  the  anterior  legs  of  "  very  many  insects," 
which  they  use  for  cleansing  their  antennae.  These,  he  argues, 
cannot  have  resulted  from  the  inheritance  of  acquired  characters ; 
since  any  supposed  changes  produced  by  function  would  be 
changes  in  the  chitinous  exo-skeleton,  which,  being  a  dead  sub- 
stance, cannot  have  had  its  changes  transmitted.  He  then  pro- 
ceeds, very  candidly,  to  point  out  the  extreme  difficulties  which 
lie  in  the  way  of  supposing  these  structures  to  have  resulted  from 
natural  selection :  admitting  that  an  opponent  might  "  say  that 
it  was  absurd  "  to  assume  that  the  successive  small  variations  im- 
plied were  severally  life-saving  in  their  effects.  Nevertheless,  he 
holds  it  unquestionable  that  natural  selection  has  been  the  cause. 
See  then  the  difference.  The  supposition  that  the  apparatus  has 
been  produced  by  the  inheritance  of  acquired  characters  is 
rejected  because  it  presents  insuperable  difficulties.  But  the 
supposition  that  the  apparatus  has  been  produced  by  natural 
selection  is  accepted,  though  it  presents  insuperable  difficulties. 

*  Contemporary  Review,  September,  1893. 


652  APPENDIX   B. 

If  this  mode  of  reasoning  is  allowable,  no  fair  comparison  be- 
tween diverse  hypotheses  can  be  made. 

With  these  remarks  on  Professor  Weismann's  method  at  large, 
let  me  now  pass  to  the  particular  arguments  he  uses,  taking  them 
seriatim. 

The  first  case  he  deals  with  is  that  of  the  progressive  degra- 
dation of  the  human  little  toe.  This  he  considers  a  good  test 
case ;  and  he  proceeds  to  discuss  an  assigned  cause — the  inherited 
and  accumulated  effects  of  boot-pressure.  Without  much  diffi- 
culty he  shows  that  this  interpretation  is  inadequate ;  since 
fusion  of  the  phalanges,  which  constitutes  in  part  the  progressive 
degradation,  is  found  among  peoples  who  go  barefoot,  and  has 
been  found  also  in  Egyptian  mummies.  Having  thus  disposed  of 
Mr.  Buckman's  interpretation,  Professor  Weismann  forthwith 
concludes  that  the  ascription  of  this  anatomical  change  to  the 
inheritance  of  acquired  characters  is  disposed  of,  and  assumes,  as 
the  only  other  possible  interpretation,  a  dwindling  "  through  pan- 
mixia " :  "  the  hereditary  degeneration  of  the  little  toe  is  thus 
quite  simply  explained  from  my  standpoint." 

It  is  surprising  that  Professor  Weismann  should  not  have  seen 
that  there  is  an  explanation  against  which  his  criticism  does  not 
tell.  If  we  go  back  to  the  genesis  of  the  human  type  from  some 
lower  type  of  primates,  we  see  that  while  the  little  toe  has  ceased 
to  be  of  any  use  for  climbing  purposes,  it  has  not  come  into  any 
considerable  use  for  walking  and  running.  A  glance  at  the  feet 
of  the  sub-human  primates  in  general,  shows  that  the  inner  digits 
are,  as  compared  with  those  of  men,  quite  small,  have  no  such 
relative  length  and  massiveness  as  the  human  great  toes.  Leav- 
ing out  the  question  of  cause,  it  is  manifest  that  the  great  toes 
have  been  immensely  developed,  since  there  took  place  the 
change  from  arboreal  habits  to  terrestrial  habits.  A  study  of  the 
mechanics  of  walking  shows  why  this  has  happened.  Stability 
requires  that  the  "  line  of  direction "  (the  vertical  line  let  fall 
from  the  centre  of  gravity)  shall  fall  within  the  base,  and,  in 
walking,  shall  be  brought  at  each  step  within  the  area  of  support, 
or  so  near  it  that  any  tendency  to  fall  may  be  checked  at  the 
next  step.  A  necessary  result  is  that  if,  at  each  step,  the  chief 
stress  of  support  is  thrown  on  the  outer  side  of  the  foot,  the  body 
must  be  swayed  so  that  the  "line  of  direction"  may  fall  within 
the  outer  side  of  the  foot,  or  close  to  it ;  and  when  the  next  step 
is  taken  it  must  be  similarly  swayed  in  an  opposite  way,  so  that 
the  outer  side  of  the  other  foot  may  bear  the  weight.  That  is  to 
say,  the  body  must  oscillate  from  side  to  side,  or  waddle.  The 
movements  of  a  duck  when  walking  or  running  show  what  hap- 
pens when  the  points  of  support  are  wide  apart.  Clearly  this 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      653 

kind  of  movement  conflicts  with  efficient  locomotion.  There  is  a 
waste  of  muscular  energy  in  making  these  lateral  movements, 
and  they  are  at  variance  with  the  forward  movement.  We  may 
infer,  then,  that  the  developing  man  profited  by  throwing  the 
stress  as  much  as  possible  on  the  inner  sides  of  the  feet ;  and  was 
especially  led  to  do  this  when  going  fast,  which  enabled  him  to 
abridge  the  oscillations  :  as  indeed  we  now  see  in  a  drunken 
man.  Thus  there  was  thrown  a  continually  increasing  stress 
upon  the  inner  digits  as  they  progressively  developed  from  the 
effects  of  use  ;  until  now  that  the  inner  digits,  so  large  compared 
with  the  others,  bear  the  greater  part  of  the  weight,  and  being 
relatively  near  one  another,  render  needless  any  marked  sway- 
ings  from  side  to  side.  But  what  has  meanwhile  happened  to  the 
outer  digits  ?  Evidently  as  fast  as  the  great  toes  have  come 
more  and  more  into  play  and  developed,  the  little  toes  have  gone 
more  and  more  out  of  play  and  have  been  dwindling  for — how 
long  shall  we  say  ? — perhaps  a  hundred  thousand  years. 

So  far,  then,  am  I  from  feeling  that  Professor  Weismann  has 
here  raised  a  difficulty  in  the  way  of  the  doctrine  1  hold,  that 
I  feel  indebted  to  him  for  having  drawn  attention  to  a  very 
strong  evidence  in  its  support.  This  modification  in  the  form  of 
the  foot,  which  has  occurred  since  arboreal  habits  have  given 
place  to  terrestrial  habits,  shows  the  effects  of  use  and  disuse 
simultaneously.  The  inner  digits  have  increased  by  use  while 
the  outer  digits  have  decreased  by  disuse. 

Saying  that  he  will  not  "  pause  to  refute  other  apparent 
proofs  of  the  transmission  of  acquired  characters,"  Professor 
Weismann  proceeds  to  deal  with  the  argument  which,  with 
various  illustrations,  I  have  several  times  urged — the  argument 
that  the  natural  selection  of  fortuitously -arising  variations  cannot 
account  for  the  adjustment  of  co-operative  parts.  Very  clearly 
and  very  fairly  he  summarises  this  argument  as  used  in  The 
Principles  of  Biology  in  1864.  Admitting  that  in  this  case  there 
are  "  enormous  difficulties  "  in  the  way  of  any  other  interpreta- 
tion than  the  inheritance  of  acquired  characters,  Professor 
Weismann  before  proceeding  to  assault  this  "  last  bulwark  of 
the  Lamarckian  principle,"  premises  that  the  inheritance  of  ac- 
quired characters  cannot  be  a  cause  of  change  because  inactive 
as  well  as  active  parts  degenerate  when  they  cease  to  be  of  use  : 
instancing  the  "  skin  and  skin-armature  of  crabs  and  insects." 
On  this  I  may  remark  in  the  first  place  that  an  argument 
derived  from  degeneracy  of  passive  structures  scarcely  meets 
the  case  of  development  of  active  structures ;  and  I  may  re- 
mark in  the  second  place  that  1  have  never  dreamt  of  denying 
the  efficiency  of  natural  selection  as  a  cause  of  degeneracy  in 


C54  APPENDIX  B. 

passive  structures  when  the  degeneracy  is  such  as  aids  the  pro- 
sperity of  the  stirp. 

Making  this  parenthetical  reply  to  his  parenthetical  criticism  I 
pass  to  his  discussion  of  this  particular  argument  which  he  un- 
dertakes to  dispose  of. 

His  cheval  de  bataille  is  furnished  him  by  the  social  insects — 
not  a  fresh  one,  however,  as  might  be  supposed  from  the  way  in 
which  he  mounts  it.  From  time  to  time  it  has  carried  other 
riders,  who  have  couched  their  lances  with  fatal  effects  as  they 
supposed.  But  I  hope  to  show  that  no  one  of  them  has  unhorsed 
an  antagonist,  and  that  Professor  Weismann  fails  to  do  this  just 
as  completely  as  his  predecessors.  I  am,  indeed,  not  sorry  that 
he  has  afforded  me  the  opportunity  of  criticising  the  general 
discussion  concerning  the  peculiarities  of  these  interesting  crea- 
tures, which  it  has  often  seemed  to  me  sets  out  with  illegitimate 
assumptions.  The  supposition  always  is  that  the  specialities  of 
structures  and  instincts  in  the  unlike  classes  of  their  communities, 
have  arisen  during  the  period  in  which  the  communities  have 
existed  in  something  like  their  present  forms.  This  cannot  be. 
It  is  doubtless  true  that  association  without  differentiations  of 
classes  may  pre-exist  for  co-operative  purposes,  as  among  wolves, 
and  as  among  various  insects  which  swarm  under  certain  circum- 
stances. Hence  we  may  suppose  that  there  arise  in  some  cases 
permanent  swarms — that  survival  of  the  fittest  will  establish  these 
constant  swarms  where  they  are  advantageous.  But  admitting 
this,  we  have  also  to  admit  a  gradual  rise  of  the  associated  state 
out  of  the  solitary  state.  Wasps  and  bees  present  us  with  grada- 
tions. If,  then,  we  are  to  understand  how  the  organized  societies 
have  arisen,  either  out  of  the  solitary  state  or  out  of  undifferen- 
tiated  swarms,  we  must  assume  that  the  differences  of  structure 
and  instinct  among  the  members  of  them  arose  little  by  little,  as 
the  social  organization  arose  little  by  little.  Fortunately  we  are 
able  to  trace  the  greater  part  of  the  process  in  the  annually- 
formed  communities  of  the  common  wasp  ;  and  we  shall  recognize 
in  it  an  all-important  factor  (ignored  by  Professor  Weismann)  to 
which  the  phenomena,  or  at  any  rate  the  greater  part  of  them, 
are  due. 

But  before  describing  the  wasp's  annual  history,  let  me  set 
down  certain  observations  made  when,  as  a  boy,  I  was  given  to 
angling,  and,  in  July  or  August,  sometimes  used  for  bait  "  wasp- 
grubs,"  as  they  were  called.  After  having  had  two  or  three 
days  the  combs  or  "  cakes  "  of  these,  full  of  unfed  larvae  in  all 
stages  of  growth,  I  often  saw  some  of  them  devouring  the  edges 
of  their  cells  to  satisfy  their  appetites ;  and  saw  others,  probably 
the  most  advanced  in  growth,  which  were  spinning  the  little 
cjvcrinj  caps  to  their  cells,  in  preparation  for  assuming  the  pupa 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      655 

state.  It  is  to  be  inferred  that  if,  after  a  certain  stage  of  growth 
has  been  reached,  the  food-supply  becomes  inadequate  or  is 
stopped  altogether,  the  larva  undergoes  its  transformation  pre- 
maturely ;  and,  as  we  shall  presently  see,  this  premature  trans- 
formation has  several  natural  sequences. 

Let  us  return  now  to  the  wasp's  family  history.  In  the  spring, 
a  queen-wasp  or  mother-wasp  which  has  survived  the  winter, 
begins  to  make  a  small  nest  containing  four  or  more  cells  in 
which  she  lays  eggs,  and  as  fast  as  she  builds  additional  cells,  she 
lays  an  egg  in  each.  Presently,  to  these  activities,  is  added  the 
feeding  of  the  larvae :  one  result  being  that  the  multiplication  of 
larvae  involves  a  restriction  of  the  food  that  can  be  given  to  each. 
If  we  suppose  that  the  mother-wasp  rears  no  more  larvae  than  she 
can  fully  feed,  there  will  result  queens  or  mothers  like  herself, 
relatively  few  in  number.  But  if  we  suppose  that,  laying  more 
numerous  eggs  she  produces  more  larvae  than  she  can  fully  feed, 
the  result  will  be  that  when  these  have  reached  a  certain  stage 
of  growth,  inadequate  supply  of  food  will  be  followed  by  pre- 
mature retirement  and  transformation  into  pupae.  What  will  be 
the  characters  of  the  developed  insects?  The  first  effect  of 
arrested  nutrition  will  be  smaller  size.  This  we  find.  A  second 
effect  will  be  defective  development  of  parts  that  are  latest  formed 
and  least  important  for  the  survival  of  the  individual.  Hence  we 
may  look  for  arrested  development  of  the  reproductive  organs — 
non-essential  to  individual  life.  And  this  expectation  is  in  accord 
with  what  we  see  in  animal  development  at  large ;  for  (passing 
over  entirely  sexless  individuals)  we  see  that  though  the  repro- 
ductive organs  may  be  marked  out  early  in  the  course  of  develop- 
ment, they  are  not  made  fit  for  action  until  after  the  structures 
for  carrying  on  individual  life -are  nearly  complete.  The  implica- 
tion is,  then,  that  an  inadequately-fed  and  small  larva  will  become 
a  sterile  imago.  Having  noted  this,  let  us  pass  to  a  remarkable 
concomitant.  In  the  course  of  development,  organs  are  formed 
not  alone  in  the  order  of  their  original  succession,  but  partly  in 
the  order  of  importance  and  the  share  they  have  to  take  in  adult 
activities — a  change  of  order  called  by  Ilaeckel  "heterochrony." 
Hence  the  fact  that  we  often  see  the  maternal  instinct  precede 
the  sexual  instinct.  Every  little  girl  with  her  doll  shows  us  that 
the  one  may  become  alive  while  the  other  remains  dormant.  In 
the  case  of  wasps,  then,  premature  arrest  of  development  may 
result  in  incompleteness  of  the  sexual  traits,  along  with  complete- 
ness of  the  maternal  traits.  What  happens  ?  Leave  out  the  lav- 
ing of  eggs,  and  the  energies  of  the  mother-wasp  are  spent  wholly 
in  building  cells  and  feeding  larv;e,  and  the  worker-wasp  forth- 
with begins  to  spend  its  life  in  building  cells  and  feeding  larv.e. 
Thus  interpretiag  the  facts,  we  have  no  occasion  to  assume  any 


656  APPENDIX   B. 

constitutional  difference  between  the  eggs  of  worker- wasps  and 
the  eggs  of  queens ;  and  that,  their  eggs  are  not  different  we  see, 
first,  in  the  fact  that  occasionally  the  worker-wasp  is  fertile  and 
lays  drone-producing  eggs,  and  we  see  secondly  that  (if  in  this 
respect  they  are  like  the  bees,  of  which,  however,  we  have  no 
proof)  the  larva  of  a  worker-wasp  can  be  changed  into  the  larva 
of  a  queen-wasp  by  special  feeding.  But  be  this  as  it  may,  we 
have  good  evidence  that  the  feeding  determines  everything.  Says 
Dr.  Ormerod,  in  his  British  Social  Wasps : — 

"When  the  swarm  is  strong  and  food  plentiful  .  .  .  the  well  fed 
larvae  develop  into  females,  full,  large,  and  overflowing  with  fat.  There  are 
all  gradations  of  size,  from  the  large  fat  female  to  the  smallest  worker.  .  .  . 
The  larger  the  wasp,  the  larger  and  better  developed,  as  the  rule,  are  the 
female  organs,  in  all  their  details.  In  the  largest  wasps,  which  are  to  be  the 
queens  of  another  year,  the  ovaries  differ  to  all  appearances  in  nothing  but 
their  size  from  those  of  the  larger  worker  wasps.  .  .  .  Small  feeble  swarms 
produce  few  or  no  perfect  females  ;  but  in  large  strong  swarms  they  are  found 
by  the  score."  (pp.  248-9) 

To  this  evidence  add  the  further  evidence  that  queens  and 
workers  pass  through  certain  parallel  stages  in  respect  of  their 
maternal  activities.  At  first  the  queen,  besides  laying  eggs,  builds 
cells  and  feeds  larvae,  but  after  a  time  ceases  to  build  cells,  and 
feeds  larvae  only,  and  eventually  doing  neither  one  nor  the  other, 
only  lays  eggs,  and  is  supplied  with  food  by  the  workers.  So  it 
is  in  part  with  the  workers.  While  the  members  of  each  succes- 
sive brood,  when  in  full  vigour,  build  cells  and  feed  larva,  by- 
and-by  they  cease  to  build  cells,  and  only  feed  larvae :  the  ma- 
ternal activities  and  instincts  undergo  analogous  changes.  In 
this  case,  then,  we  are  not  obliged  to  assume  that  only  by  a  pro- 
cess of  natural  selection  can  the  differences  of  structure  and  in- 
stinct between  queens  and  workers'  be  produced.  The  only  way 
in  which  natural  selection  here  comes  into  play  is  in  the  better 
survival  of  the  families  of  those  queens  which  made  as  many 
cells,  and  laid  as  many  eggs,  as  resulted  in  the  best  number  of 
half-fed  larvae,  producing  workers ;  since  by  a  rapid  multiplica- 
tion of  workers  the  family  is  advantaged,  and  the  ultimate  pro- 
duction of  more  queens  surviving  into  the  next  year  insured. 

The  differentiation  of  classes  does  not  go  far  among  the  wasps, 
because  the  cycle  of  processes  is  limited  to  a  year,  or  rather  to 
the  few  months  of  the  summer.  It  goes  further  among  the  hive- 
bees,  which,  by  storing  food,  survive  from  one  year  into  the  next. 
Unlike  the  queen-wasp,  the  queen-bee  neither  builds  cells  nor 
gathers  food,  but  is  fed  by  the  workers :  egg  laying  has  become 
her  sole  business.  On  the  other  hand  the  workers,  occupied  ex- 
clusively in  building  and  nursing,  have  the  reproductive  organs 
more  dwarfed  than  they  are  in  wasps.  Still  we  see  that  the 
worker-bee  occasionally  lays  drone-producing  eggs,  and  that,  by 


INADEQUACY  OP  NATURAL  SELECTION,  ETC.      007 

giving  extra  nutriment  and  the  required  extra  space,  a  worker- 
larva  can  be  developed  into  a  queen- larva.  In  respect  to  the 
leading  traits,  therefore,  the  same  interpretation  holds.  Doubt- 
less there  are  subsidiary  instincts  which  are  apparently  not  thus 
interpretable.  But  before  it  can  be  assumed  that  an  interpreta- 
tion of  another  kind  is  necessary,  it  must  be  shown  that  these 
instincts  cannot  be  traced  back  to  those  pre-social  types  and  semi- 
social  types  which  must  have  preceded  the  social  types  we  now 
see.  For  unquestionably  existing  bees  must  have  brought  with 
them  from  the  pre-social  state  an  extensive  endowment  of  in- 
stincts, and,  acquiring  other  instincts  during  the  unorganized 
social  state,  must  have  brought  these  into  the  present  organized 
social  state.  It  is  clear,  for  instance,  that  the  cell-building  in- 
stinct in  all  its  elaboration  was  mainly  developed  in  the  pre-social 
stage ;  for  the  transition  from  species  building  solitary  cells  to 
those  building  combs  is  traceable.  We  are  similarly  enabled  to 
account  for  swarming  as  being  an  inheritance  from  remote  ances- 
tral types.  For  just  in  the  same  way  that,  with  under-feeding  of 
larvae,  there  result  individuals  with  imperfectly  developed  repro- 
ductive systems,  so  there  will  result  individuals  with  imperfect 
sexual  instincts ;  and  just  as  the  imperfect  reproductive  system 
partially  operates  upon  occasion,  so  will  the  imperfect  sexual  in- 
stinct. Whence  it  will  result  that  on  the  event  which  causes  a 
queen  to  undertake  a  nuptial  flight  which  is  effectual,  the  workers 
may  take  abortive  nuptial  flights :  so  causing  a  swarm. 

And  here,  before  going  further,  let  us  note  an  instructive  class 
of  facts  related  to  the  class  of  facts  above  set  forth.  Summing 
up,  in  a  chapter  on  "  The  Determination  of  Sex,"  an  induction 
from  many  cases,  Professor  Geddes  and  Mr.  Thompson  remark 
that  "such  conditions  as  deficient  or  abnormal  food,"  and  others 
causing  "  preponderance  of  waste  over  repair  ....  tend  to 
result  in  production  of  males ;  "  while  "  abundant  and  rich  nutri- 
tion "  and  other  conditions  which  "  favour  constructive  processes 
result  in  the  production  of  females."  *  Among  such 
evidences  of  this  as  immediately  concern  us,  are  these  : — J.  II. 
Fabre  found  that  in  the  nests  of  Osmia  tricornis,  eggs  at  the 
bottom,  first  laid,  and  accompanied  by  much  food,  produced 
females,  while  those  at  the  top,  last  laid,  and  accompanied  by  one- 
half  or  one-third  the  quantity  of  food,  produced  males. f  Huber's 
observations  on  egg-laying  by  the  honey-bee,  show  that  in  the 
normal  course  of  things,  the  queen  lays  eggs  of  workers  for  eleven 
months,  and  only  then  lays  eggs  of  drones :  that  is,  when  de- 
clining nutrition  or  exhaustion  has  set  in.  Further,  we  have  the 
above-named  fact,  shown  by  wasps  and  bees,  that  when  workers 

*  Evolution  of  Sex,  p.  50. 

f  Souvenirs  Entomologiques,  3me  Serie,  p.  328. 


05 S  APPENDIX  B. 

Iry  eggs  these  produce  drones  only.*  Special  evidence,  harmon- 
izing with  general  evidence,  thus  proves  that  among  the  social 
insects  the  sex  is  determined  by  degree  of  nutrition  while  the  egg 
is  being  formed.  See  then  how  congruous  this  evidence  is  with 
the  conclusion  above  drawn ;  for  it  is  proved  that  after  an  egg, 
predetermined  as  a  female,  has  been  laid,  the  character  of  the 
produced  insect  as  a  perfect  female  or  imperfect  female  is  deter- 
mined by  the  nutrition  of  the  larva.  That  is,  one  set  of  differences 
in  structures  and  instincts  is  determined  by  nutrition  before  the  egg 
is  laid,  and  a  further  set  of  differences  in  structures  and  instincts  is 
determined  by  nutrition  after  the  egg  is  laid. 

We  come  now  to  the  extreme  case — that  of  the  ants.  Is  it 
not  probable  that  the  process  of  differentiation  has  been  similar  ? 
There  are  sundry  reasons  for  thinking  so.  With  ants  as  with 
wasps  and  bees — the  workers  occasionally  lay  eggs ;  and  an  ant- 
community  can,  like  a  bee-community,  when  need  be,  produce 
queens  out  of  worker-larvae :  presumably  in  the  same  manner  by 
extra  feeding.  But  here  we  have  to  add  special  evidence  of  great 
significance.  For  observe  that  the  very  facts  concerning  ants, 
which  Professor  Weismann  names  as  exemplifying  the  formation 
of  the  worker  type  by  selection,  serve,  as  in  the  case  of  wasps,  to 
exemplify  its  formation  by  arrested  nutrition.  He  says  that  in 
several  species  the  egg-tubes  in  the  ovaries  show  progressive 
decrease  in  number ;  and  this,  like  the  different  degrees  of  arrest 
in  the  ovaries  of  the  worker-wasps,  indicates  arrest  of  larva- 
feeding  at  different  stages.  He  gives  cases  showing  that,  in 
different  degrees,  the  eyes  of  workers  are  less  developed  in  the 
number  of  their  facets  than  those  of  the  perfect  insects;  and 
he  also  refers  to  the  wings  of  workers  as  not  being  developed : 
remarking,  however,  that  the  rudiments  of  their  wings  show  that 
the  ancestral  forms  had  wings.  Are  not  these  traits  also  results 
of  arrested  nutrition  ?  Generally  among  insects  the  larvae  are 
either  blind  or  have  but  rudimentary  eyes  ;  that  is  to  say,  visual 
organs  are  among  the  latest  organs  to  arise  in  the  genesis  of 
the  perfect  organism.  Hence  early  arrest  of  nutrition  will  stop 
formation  of  these,  while  various  more  ancient  structures  have 
become  tolerably  complete.  Similarly  with  wings.  Wings  are 
late  organs  in  insect  phylogeny,  and  therefore  will  be  among 
those  most  likely  to  abort  where  development  is  prematurely 
arrested.  And  both  these  traits  will,  for  the  same  reason,  natu- 
rally go  along  with  arrested  development  of  the  reproductive 
system.  Even  more  significant,  however,  is  some  evidence  as- 
signed by  Mr.  Darwin  respecting  the  caste-gradations  among  the 
driver  ants  of  West  Africa.  He  says  : — 

*  Natural  History  of  Sees,  new  ed.,  p.  33. 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      G59 

"  But  the  most  important  fact  for  us  is,  that,  though  the  workers  c-n  be 
grouped  into  castes  of  diiferent  sizes,  yet  they  graduate  insensibly  into  each 
other,  as  does  the  widely-different  structure  of  their  jaws."  * 

"  Graduate  insensibly,"  lie  says  ;  implying  that  there  are  very 
numerous  intermediate  forms.  This  is  exactly  what  is  to  be 
expected  if  arrest  of  nutrition  be  the  cause  ;  for  unless  the  ants 
have  definite  measures,  enabling  them  to  stop  feeding  at  just  the 
same  stages,  it  must  happen  that  the  stoppage  of  feeding  will  be 
indefinite ;  and  that,  therefore,  there  will  be  all  gradations 
between  the  extreme  forms — "  insensible  gradations,"  both  in  size 
and  in  jaw-structure. 

In  contrast  with  this  interpretation,  consider  now  that  of 
Professor  Weismann.  From  whichever  of  the  two  possible  sup- 
positions he  sets  out,  the  result  is  equally  fatal.  If  he  is  con- 
sistent, he  must  say  that  each  of  these  "intermediate  forms  of 
workers  must  have'its  special  set  of  "  determinants,"  causing  its 
special  set  of  modifications  of  organs  ;  for  he  cannot  assume  that 
while  perfect  females  and  the  extreme  types  of  workers  have 
their  different  sets  of  determinants,  the  intermediate  types  of 
workers  have  not.  Hence  we  are  introduced  to  the  strange  con- 
clusion that  besides  the  markedly-distinguished  sets  of  determi- 
nants there  must  be,  to  produce  these  intermediate  forms,  many 
other  sets  slightly  distinguished  from  one  another — a  score  or 
more  kinds  of  germ-plasm  in  addition  to  the  four  chief  kinds. 
Next  comes  an  introduction  to  the  still  stranger  conclusion,  that 
these  numerous  kinds  of  germ-plasm,  producing  these  numerous 
intermediate  forms,  are  not  simply  needless  but  injurious — pro- 
duce forms  not  well  fitted  for  either  of  the  functions  discharged 
by  the  extreme  forms  :  the  implication  being  that  natural  selec- 
tion has  originated  these  disadvantageous  forms  !  If  to  escape 
from  this  necessity  for  suicide,  Professor  Weismann  accepts  the 
inference  that  the  differences  among  these  numerous  intermediate 
forms  are  caused  by  arrested  feeding  of  the  larvae  at  different 
stages,  then  he  is  bound  to  admit  that  the  differences  between 
the  extreme  forms,  and  between  these  and  perfect  females,  are 
similarly  caused.  But  if  he  does  this,  what  becomes  of  his  hypo- 
thesis that  the  several  castes  are  constitutionally  distinct,  and 
result  from  the  operation  of  natural  selection  ?  Observe,  too, 
that  his  theory  does  not  even  allow  him  to  make  this  choice ;  for 
we  have  clear  proof  that  unlikenesses  among  the  forms  of  the  same 
species  cannot  be  determined  this  way  or  that  way  by  differences 
of  nutrition.  English  greyhounds  and  Scotch  greyhounds  do  not 
differ  from  one  another  so  much  as  do  the  Amazon-workers  from 
the  inferior  workers,  or  the  workers  from  the  queens.  But  no 

*  Origin  of  Species,  6th  ed.,  p.  232. 


660  APPENDIX  B. 

matter  how  a  pregnant  Scotch  greyhound  is  fed,  or  her  pups  after 
they  are  born,  they  cannot  be  changed  into  English  greyhounds : 
the  different  germ-plasms  assert  themselves  spite  of  all  treatment. 
But  in  these  social  insects  the  different  structures  of  queens  and 
workers  are  determinable  by  differences  of  feeling.  Therefore 
the  production  of  their  various  castes  does  not  result  from  the 
natural  selection  of  varying  germ-plasm. 

Before  dealing  with  Professor  Weismann's  crucial  case — that 
co -adaptation  of  parts,  which,  in  the  soldier-ants,  has,  he  thinks, 
arisen  without  inheritance  of  acquired  characters — let  me  deal 
with  an  ancillary  care  which  he  puts  forward  as  explicable  by 
"panmixia  alone."  This  is  the  "degeneration,  in  the  warlike 
Amazon-ants,  of  the  instinct  to  search  for  food."  *  Let  us  first 
ask  what  have  been  the  probable  antecedents  of  these  Amazon- 
ants  ;  for,  as  I  have  above  said,  it  is  absurd  to  speculate  about 
the  structures  and  instincts  the  species  possesses  in  its  existing 
organized  social  state  without  asking  what  structures  and  in- 
stincts it  brought  with  it  from  its  original  solitary  state  and  its 
unorganized  social  state.  From  the  outset  these  ants  were  pre- 
datory. Some  variety  of  them  led  to  swarm — probably  at  the 
sexual  season — did  not  again  disperse  so  soon  as  other  varie- 
ties. Those  which  thus  kept  together  derived  advantages  from 
making  simultaneous  attacks  on  prey,  and  prospered  accordingly. 
Of  descendants  the  varieties  which  carried  on  longest  the 
associated  state  prospered  most ;  until,  at  length,  the  associated 
state  became  permanent.  All  which  social  progress  took  place 
while  there  existed  only  perfect  males  and  females.  What 
was  the  next  step  ?  Ants  utilize  other  insects,  and,  among 
other  ways  of  doing  this,  sometimes  make  their  nests  where  there 
are  useful  insects  ready  to  be  utilized.  Giving  an  account  of 
certain  New  Zealand  species  of  Tetramorium,  Mr.  W.  W.  Smith 
says  they  seek  out  underground  places  where  there  are  "  root- 
feeding  aphides  and  coccids,"  which  they  begin  to  treat  as 
domestic  animals ;  and  further  he  says  that  when,  after  the 
pairing  season,  new  nests  are  being  formed,  there  are  "  a  few 
ants  of  both  sexes  .  .  .  from  two  up  to  eight  or  ten."  f 
Carrying  with  us  this  fact  as  a  key,  let  us  ask  what  habits  will 
be  fallen  into  by  the  conquering  species  of  ants.  They,  too,  wih 
seek  places  where  there  are  creatures  to  be  utilized  ;  and,  finding 
it  profitable,  will  invade  the  habitations  not  of  defenceless  crea- 
tures only,  but  of  creatures  whose  powers  of  defence  are  inade- 
quate— weaker  species  of  their  own  order.  A  very  small 
modification  will  affiliate  their  habits  on  habits  of  their  proto- 
types. Instead  of  being  supplied  with  sweet  substance  excreted 

*  Contemporary  Revieio,  September,  1893,  p.  333. 

f  T/ic  Entomologist's  Monthly  Magazine,  March,  1892,  p.  61. 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      661 

by  the  aphides  they  are  supplied  with  sweet  substance  by  the 
ants  among  which  they  parasitically  settle  themselves.  How 
easily  the  subjugated  ants  may  fall  into  the  habit  of  feeding 
them,  we  shall  see  on  remembering  that  already  they  feed  not 
only  larvae  but  adults — individuals  bigger  than  themselves.  And 
that  attentions  kindred  to  these  paid  to  parasitic  ants  may  be 
established  without  difficulty,  is  shown  us  by  the  small  birds 
which  continue  to  feed  a  young  cuckoo  in  their  nest  when  it  has 
outgrown  them.  This  advanced  form  of  parasitism  grew  up 
while  there  were  yet  only  perfect  males  and  females,  as  happens 
in  the  initial  stage  with  these  New  Zealand  ants.  What  further 
modifications  of  habits  were  probably  then  acquired  ?  Frem  the 
practice  of  settling  themselves  where  there  already  exist  colonies 
of  aphides,  which  they  carry  about  to  suitable  places  in  the  nest, 
like  Tetramorium,  other  ants  pass  to  the  practice  of  making  ex- 
cursions to  get  aphides,  and  putting  them  in  better  feeding  places 
where  they  become  more  productive  of  saccharine  matter.  By  a 
parallel  step  these  soldier-ants  pass  from  the  stage  of  settling 
themselves  among  other  ants  which  feed  them,  to  the  stage  of 
fetching  the  pupae  of  such  ants  to  the  nest :  a  transition  like  that 
which  occurs  among  slave-making  human  beings.  Thus  by  pro- 
cesses analogous  to  those  we  see  going  on,  these  communities  of 
slave-making  ants  may  be  formed.  And  since  the  transition 
from  an  unorganized  social  state  to  a  social  state  characterized 
by  castes,  must  have  been  gradual,  there  must  have  been  a  long 
interval  during  which  the  perfect  males  and  females  of  these 
conquering  ants  could  acquire  habits  and  transmit  them  to 
progeny.  A  small  modification  accounts  for  that  seemingly- 
strange  habit  which  Professor  Weismann  signalizes.  For  if,  as 
is  observed,  those  ants  which  keep  aphides  solicit  them  to  excrete 
a  supply  of  ant-food  by  stroking  them  with  the  antennae,  they 
come  very  near  to  doing  that  which  Professor  Weismann  says  the 
soldier-ants  do  towards  a  worker — "  they  come  to  it  and  beg  for 
food  :  "  the  food  being  put  into  their  mouths  in  this  last  case  as 
almost  or  quite  in  the  first.  And  evidently  this  habit  of  passively 
receiving  food,  continued  through  many  generations  of  perfect 
males  and  females,  may  result  in  such  disuse  of  the  power  of 
self -feeding  that  this  is  eventually  lost.  The  behaviour  of  young 
birds,  during,  and  after,  their  nest-life,  gives  us  the  clue.  For  a 
week  or  more  after  they  are  full-grown  and  fly  about  with  their 
parents,  they  may  be  seen  begging  for  food  and  making  no  efforts 
to  recognize  and  pick  up  food  for  themselves.  If,  generation 
after  generation,  feeding  of  them  in  full  measure  continued,  they 
would  not  learn  to  feed  themselves  :  the  perceptions  and  instincts 
implied  in  self-feeding  would  be  later  and  later  developed,  until, 
with  entire  disuse  of  them,  they  would  disappear  altogether  by 
43 


062  APPENDIX  B. 

inheritance.  Thus  self-feeding  may  readily  have  ceased  among 
these  soldier-ants  before  the  caste-organization  arose  among  them. 
With  this  interpretation  compare  the  interpretation  of  Pro- 
fessor Weismann.  I  have  before  protested  against  arguing  in 
abstracts  without  descending  to  concretes.  Here  let  us  ask  what 
are  the  particular  changes  which  the  alleged  explanation  by  sur- 
vival of  the  fittest  involves.  Suppose  we  make  the  very  liberal 
supposition  that  an  ant's  central  ganglion  bears  to  its  body  the 
same  ratio  as  the  human  brain  bears  to  the  human  body — say, 
one-fortieth  of  its  weight.  Assuming  this,  what  shall  we  assume 
to  be  the  weight  of  those  ganglion-cells  and  fibres  in  which  are 
localized  the  perceptions  of  food  and  the  suggestion  to  take  it  ? 
Shall  we  say  that  these  amount  to  one-tenth  of  the  central 
ganglion  ?  This  is  a  high  estimate  considering  all  the  impres- 
sions which  this  ganglion  has  to  receive,  and  all  the  operations 
which  it  has  to  direct.  Still  we  will  say  one-tenth.  Then  it 
follows  that  this  portion  of  nervous  substance  is  one-400th  of  the 
weight  of  its  body.  By  what  series  of  variations  shall  we  say 
that  it  is  reduced  from  full  power  to  entire  incapacity  ?  Shall 
we  say  five  ?  This  is  a  small  number  to  assume.  Nevertheless 
we  will  assume  it.  What  results  ?  That  the  economy  of  nerve- 
substance  achieved  by  each  of  these  five  variations  will  amount  to 
one-2000th  of  the  entire  mass.  Making  these  highly  favourable 
assumptions,  what  follows  : — The  queen-ant  lays  eggs  that  give 
origin  to  individuals  in  each  of  which  there  is  achieved  an 
economy  in  nerve-substance  of  one-2000th  of  its  weight ;  and 
the  implication  of  the  hypothesis  is  that  such  an  economy  will  so 
advantage  this  ant-community  that  in  the  competition  with  other 
ant-communities  it  will  conquer.  For  here  let  me  recall  the 
truth  before  insisted  upon,  that  natural  selection  can  operate  only 
on  those  variations  which  appreciably  benefit  the  stirp.  Bearing 
in  mind  this  requirement,  is  any  one  now  prepared  to  say  that 
survival  of  the  fittest  can  cause  this  decline  of  the  self-feeding 
faculty  ?  * 

Not  limiting  himself  to  the  Darwinian  interpretation,  however, 
Professor  Weismann  says  that  this  degradation  may  be  accounted 
for  by  "  panmixia  alone."  Here  I  will  not  discuss  the  adequacy 

*  Perhaps  it  will  be  alleged  that  nerve-matter  is  costly,  and  that  this 
minute  economy  might  be  of  importance.  Anyone  who  thinks  this  will  no 
longer  think  it  after  contemplating  a  litter  of  half-a-dozen  young  rabbits  (in 
the  wild  rabbit  the  number  varies  from  four  to  eight) ;  and  on  remembering 
that  the  nerve-matter  contained  in  their  brains  and  spinal  cords,  as  well  as 
the  materials  for  building  up  the  bones,  muscles,  and  viscera  of  their  bodies, 
has  been  supplied  by  the  doe  in  the  space  of  a  month;  at  the  same 
time  that  she  has  sustained  herself  and  carried  on  her  activities:  all  this 
being  done  on  relatively  poor  food.  Nerve-matter  cannot  be  so  very  costly 
then. 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      G63 

of  this  supposed  cause,  but  will  leave  it  to  be  dealt  with  by  im- 
plication a  few  pages  in  advance,  where  the  general  hypothesis  of 
panmixia  will  be  reconsidered. 

And  now,  at  length,  we  are  prepared  for  dealing  with  Professor 
Weismann's  crucial  case — with  his  alleged  disproof  that  co-adapta- 
tion of  co-operative  parts  results  from  inheritance  of  acquired 
characters,  because  in  the  case  of  the  Amazon-ants,  it  has  arisen 
where  the  inheritance  of  acquired  characters  is  impossible.  For 
after  what  has  been  said,  it  will  be  manifest  that  the  whole  ques- 
tion is  begged  when  it  is  assumed  that  this  co-adaptation  has 
arisen  since  there  existed  among  these  ants  an  organized  social 
state.  Unquestionably  this  organized  social  state  pre-supposes  a 
series  of  modifications  through  which  it  has  been  reached.  It 
follows,  then,  that  there  can  be  no  rational  interpretation  without 
a  preceding  inquiry  concerning  that  earlier  state  in  which  there 
were  no  castes,  but  only  males  and  females.  What  kinds  of 
individuals  were  the  ancestral  ants — at  first  solitary,  and  then 
semi-social  ?  They  must  have  had  marked  powers  of  offence  and 
defence.  Of  predacious  creatures,  it  is  the  more  powerful  which 
form  societies,  not  the  weaker.  Instance  human  races.  Nations 
originate  from  the  relatively  warlike  tribes,  not  from  the  rela- 
tively peaceful  tribes.  Among  the  several  types  of  individuals 
forming  the  existing  ant  community,  to  which,  then,  did  the 
ancestral  ants  bear  the  greatest  resemblance  ?  They  could  not 
have  been  like  the  queens,  for  these,  now  devoted  to  egg-laying, 
are  unfitted  for  conquest.  They  could  not  have  been  like  the 
inferior  class  of  workers,  for  these,  too,  are  inadequately  armed 
and  lack  strength.  Hence  they  must  have  been  most  like  these 
Amazon-ants  or  soldier-ants,  which  now  make  predatory  excur- 
sions— which  now  do,  in  fact,  what  their  remote  ancestors  did. 
What  follows  ?  Their  co-adapted  parts  have  not  been  produced 
by  the  selection  of  variations  within  the  ant-community,  such  as 
we  now  see  it.  They  have  been  inherited  from  the  pre-social  and 
early  social  types  of  ants,  in  which  the  co-adaptation  of  parts  had 
been  effected  by  inheritance  of  acquired  characters.  It  is  not 
that  the  soldier-ants  have  gained  these  traits ;  it  is  that  the  other 
castes  have  lost  them.  Early  arrest  of  development  causes  ab- 
sence of  them  in  the  inferior  workers;  and  from  the  queens 
they  have  slowly  disappeared  by  inheritance  of  the  effects  of 
disuse.  For,  in  conformity  with  ordinary  facts  of  development, 
we  may  conclude  that  in  a  larva  which  is  being  so  fed  as  that  the 
development  of  the  reproductive  organs  is  becoming  pronounced, 
there  will  simultaneously  commence  arreet  in  the  development  of 
those  organs  which  are  not  to  be  used.  There  are  abundant 
proofs  that  along  with  rapid  growth  Q£  some  organs  others  abort. 
And  if  these  inferences  are  true,  then  Professor  Weismann's  argu- 


664  APPENDIX  B. 

incut  falls  to  ,he  ground.  Nay,  it  falls  to  the  ground  even  if  con- 
clusions so  definite  as  these  be  not  insisted  upon ;  for  before  he 
can  get  a  basis  for  his  argument  he  must  give  good  reasons  for 
concluding  that  these  traits  of  the  Amazon-ants  have  not  been 
inherited  from  remote  ancestors. 

One  more  step  remains.  Let  us  grant  him  his  basis,  and  lot 
us  pass  from  the  above  negative  criticism  to  a  positive  criticism. 
As  before,  I  decline  to  follow  the  practice  of  talking  in  abstracts 
instead  of  in  concretes,  and  contend  that,  difficult  as  it  may  be  to 
see  how  natural  selection  has  in  all  cases  operated,  we  ought,  at 
any  rate,  to  trace  out  its  operation  whenever  we  can,  and  see. 
where  the  hypothesis  lands  us.  According  to  Professor  Weis- 
mann's  admission,  for  production  of  the  Amazon-ant  by  natural 
selection,  "many  parts  must  have  varied  simultaneously  and  in 
harmony  with  one  another ; "  *  and  he  names  as  such,  larger 
jaws,  muscles  to  move  them,  larger  head,  and  thicker  chitin  for 
it,  bigger  nerves  for  the  muscles,  bigger  motor  centres  in  the 
brain,  and,  for  the  support  of  the  big  head,  strengthening  of  the 
thorax,  limbs,  and  skeleton  generally.  As  he  admits,  all  these 
parts  must  have  varied  simultaneously  in  due  proportion  to  one 
another.  What  must  have  been  the  proximate  causes  of  their 
variations  ?  They  must  have  been  variations  in  what  he  calls  the 
"  determinants."  He  says : — 

"We  have,  however,  to  deal  with  the  transmission  of  parts  which  are 
variable  and  this  necessitates  the  assumption  that  just  as  many  independent 
and  variable  parts  exist  in  the  germ-plasm  as  are  present  in  the"  fully  formed 
organism."  f 

Consequently  to  produce  simultaneously  these  many  variations 
of  parts,  adjusted  in  their  sizes  and  shapes,  there  must  have 
simultaneously  arisen  a  set  of  corresponding  variations  in  the 
"  determinants  "  composing  the  germ-plasm.  What  made  them 
simultaneously  vary  in  the  requisite  ways  ?  Professor  Weismann 
will  not  say  that  there  was  somewhere  a  foregone  intention. 
This  would  imply  supernatural  agency.  He  makes  no  attempt 
to  assign  a  physical  cause  for  these  simultaneous  appropriate 
variations  in  the  determinants :  an  adequate  physical  cause  being 
inconceivable.  WThat,  then,  remains  as  the  only  possible  inter- 
pretation ?  Nothing  but  a  fortuitous  concourse  of  variations  j  re- 
minding us  of  the  old  "  fortuitous  concourse  of  atoms."  Nay, 
indeed,  it  is  the  very  same  thing.  For  each  of  the  "  determinants," 
made  up  of  "biophors,"  and  these  again  of  protein-molecules,  and 
these  again  of  simpler  chemical  molecules,  must  have  had  its 
molecular  constitution  changed  in  the  required  way ;  and  the 
molecular  constitutions  of  all  the  "  determinants,"  severally  modi- 
fied differently,  but  in  adjustment  to  one  another,  must  have  been 
*  Loc.  cit.,  p.  318.  f  The  Germ  Plasm,  p.  54. 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      665 

thus  modified  by  "  a  fortuitous  concourse  of  atoms."  Now  if  this 
is  an  allowable  supposition  in  respect  of  the  "  determinants,"  and 
the  varying  organs  arising  from  them,  why  is  it  not  an  allow- 
able supposition  in  respect  of  the  organism  as  a  whole  ?  Why  not 
assume  "  a  fortuitous  concourse  of  atoms  "  in  its  broad,  simple 
form  ?  Nay,  indeed,  would  not  this  be  much  the  easier  ?  For 
observe,  this  co-adaptation  of  numerous  co-operative  parts  is  not 
achieved  by  one  set  of  variations,  but  is  achieved  gradually  by  a 
series  of  such  sets.  That  is  to  say,  the  "  fortuitous  concourse  of 
atoms  "  must  have  occurred  time  after  time  in  appropriate  ways. 
We  have  not  one  miracle,  but  a  series  of  miracles  ! 

Of  the  two  remaining  points  in  Professor  Weismann's  first 
article  which  demand  notice,  one  concerns  his  reply  to  my  argu- 
ment drawn  from  the  distribution  of  tactual  discriminativeness.  In 
what  way  does  he  treat  this  argument  ?  He  meets  it  by  an  argu- 
ment derived  from  hypothetical  evidence — not  actual  evidence. 
Taking  the  case  of  the  tongue-tip,  1  have  carefully  inquired 
whether  its  extreme  power  of  tactual  discrimination  can  give  any 
life-saving  advantage  in  moving  about  the  food  during  mastica- 
tion, in  detecting  foreign  bodies  in  it,  or  for  purposes  of  speech ; 
and  have,  I  think,  shown  that  the  ability  to  distinguish  between 
points  one  twenty-fourth  of  an  inch  apart  is  useless  for  such  pur- 
poses. Professor  Weismann  thinks  he  disposes  of  this  by  observ- 
ing that  among  the  apes  the  tongue  is  used  as  an  organ  of  touch. 
But  surely  a  counter-argument  equivalent  in  weight  to  mine 
should  have  given  a  case  in  which  power  to  discriminate  between 
points  one  twenty-fourth  of  an  inch  apart  instead  of  one-twentieth 
of  an  inch  apart  (a  variation  of  one-sixth)  had  a  life-saving 
efficacy ;  or,  at  any  rate,  should  have  suggested  such  a  case. 
Nothing  of  the  kind  is  done  or  even  attempted.  But  now  note 
that  his  reply,  accepted  even  as  it  stands,  is  suicidal.  For  what 
has  the  trusted  process  of  panmixia  been  doing  ever  since  the 
human  being  began  to  evolve  from  the  ape  ?  Why  during  thou- 
sands of  generations  has  not  the  nervous  structure  giving  this 
extreme  discriminativeness  dwindled  away  ?  Even  supposing  it 
had  been  proved  of  life-saving  efficacy  to  our  simian  ancestors,  it 
ought,  according  to  Professor  Weismann's  own  hypothesis,  to 
have  disappeared  in  us. ,  Either  there  was  none  of  the  assumed 
special  capacity  in  the  ape's  tongue,  in  which  case  his  reply  fails, 
or  panmixia  has  not  operated,  in  which  case  his  theory  of  degene- 
racy fails. 

All  this,  however,  is  but  preface  to  the  chief  answer.  The 
argument  drawn  from  the  case  of  the  tongue-tip,  with  which 
alone  Professor  Weismann  deals,  is  but  a  small  part  of  my  argu- 
ment, the  remainder  of  which  he  does  not  attempt  to  touch — 


666  APPENDIX  B. 

does  not  even  mention.  Had  I  never  referred  to  the  tongue-tip 
at  all,  the  various  contrasts  in  discriminativeness  which  I  have 
named,  between  the  one  extreme  of  the  forefinger-tip  and  the 
other  extreme  of  the  middle  of  the  back,  would  have  abundantly 
sufficed  to  establish  my  case — would  have  sufficed  to  show  the  in- 
adequacy of  natural  selection  as  a  key  and  the  adequacy  of  the 
inheritance  of  acquired  characters. 

It  seems  to  me,  then,  that  judgment  must  go  against  him  by 
default.  Practically  he  leaves  the  matter  standing  just  where 
it  did.* 

*  While  Professor  Weismann  has  not  dealt  with  my  argument  derived 
from  the  distribution  of  discriminativeness  on  the  skin,  it  has  been  criticized 
by  Mr.  McKeen  Cattell,  in  the  last  number  of  Mind  (October,  1893).  His 
general  argument,  vitiated  by  extreme  misconceptions,  I  need  not  deal 
with.  He  says  : — "  Whether  changes  acquired  by  the  individual  are 
hereditary,  and  if  so  to  what  extent,  is  a  question  of  great  interest  for  ethics 
no  less  than  for  biology.  But  Mr.  Spencer's  application  of  this  doctrine 
to  account  for  the  origin  of  species  [!]  simply  begs  the  question.  He 
assumes  useful  variations  [!] — whether  of  structure  or  habit  is  immaterial 
— without  attempting  to  explain  their  origin  " :  two  absolute  misstatemcnts 
in  two  sentences!  The  only  part  of  Mr.  Cattell's  criticism  requiring  reply 
is  that  which  concerns  the  "  sensation-areas  "  on  the  skin.  He  implies  that 
since  Weber,  experimental  psychologists  have  practically  set  aside  the 
theory  of  sensation  areas:  showing,  among  other  things,  that  relatively 
great  accuracy  of  discrimination  can  be  quickly  acquired  by  "increased 
interest  and  attention.  .  .  .  Practice  for  a  few  minutes  will  double  the 
accuracy  of  discrimination,  and  practice  on  one  side  of  the  body  is  carried 
over  to  the  other."  To  me  it  seems  manifest  that  "  increased  interest  and 
attention "  will  not  enable  a  patient  to  discriminate  two  points  where  a  few 
minutes  before  he  could  perceive  only  one.  That  which  he  can  really  do 
in  this  short  time  is  to  learn  to  discriminate  between  the  massiveness  of  a 
sensation,  produced  by  two  points  and  the  massiveness  of  that  produced  by 
one,  and  to  infer  one  point  or  two  points  accordingly.  Respecting  the 
existence  of  sensation-areas  marked  off  from  one  another,  I  may,  in  the 
first  place,  remark  that  since  the  eye  originates  as  a  dermal  sac,  and  since 
its  retina  is  a  highly  developed  part  of  the  sensitive  surface  at  large,  and 
since  the  discriminative  power  of  the  retina  depends  on  the  division  of  it 
into  numerous  rods  and  cones,  each  of  which  gives  a  separate  sensation- 
area,  it  would  be  strange  were  the  discriminative  power  of  the  skin  at  large 
achieved  by  mechanism  fundamentally  different.  In  the  second  place  I 
may  remark  that  if  Mr.  Cattell  will  refer  to  Professor  Gustav  Retzius's 
JBiohffische  Untersuchungen,  New  Series,  vol.  iv  (Stockholm,  1892),  he  will 
see  elaborate  diagrams  of  superficial  nerve  endings  in  various  animals  show- 
ing many  degrees  of  separateness.  I  guarded  myself  against  being  supposed 
to  think  that  the  sensation-areas  are  sharply  marked  off  from  one  another ; 
and  suggested,  contrariwise,  that  probably  the  branching  nerve-terminations 
intruded  among  the  branches  of  adjacent  nerve-terminations.  Here  let  me 
add  that  the  intrusion  may  vary  greatly  in  extent ;  and  that  where  the  intrud- 
ing fibres  run  far  among  those  of  adjacent  areos,  the  discriminativeness  will 
be  but  small,  while  it  will  be  great  in  proportion  as  each  set  of  branching 
fibres  is  restricted  more  nearly  to  its  own  area.  All  the  facts  are  explicable 
on  this  supposition. 


INADEQUACY  OP  NATURAL  SELECTION,   ETC.       667 

The  other  remaining  point  concerns  the  vexed  question  of 
panmixia.  Confirming  the  statement  of  Dr.  Romanes,  Professor 
Weismann  says  that  I  have  misunderstood  him.  Already  (Con- 
temporary fieview,  May,  1893,  p.  758,  and  Reprint,  p.  66)  I  have 
quoted  passages  which  appeared  to  justify  my  interpretation, 
arrived  at  after  much  seeking.*  Already,  too,  in  this  review 
(July,  1893,  p.  54)  I  have  said  why  I  did  not  hit  upon  the  inter- 
pretation now  said  to  be  the  true  one :  I  never  supposed  that  any 
one  would  assume,  without  assigned  cause,  that  (apart  from  the 
excluded  influence  of  disuse)  the  minus  variations  of  a  disused 
organ  are  greater  than  the  plus  variations.  This  was  a  tacit 
challenge  to  produce  reasons  for  the  assumption.  Professor 
Weismann  does  not  accept  the  challenge,  but  simply  says : — "  In 
my  opinion  all  organs  are  maintained  at  the  height  of  their  de- 
velopment only  through  uninterrupted  selection "  (p.  332) :  in 
the  absence  of  which  they  decline.  Now  it  is  doubtless  true  that 
as  a  naturalist  he  may  claim  for  his  "  opinion  "  a  relatively  great 
weight.  Still,  in  pursuance  of  the  methods  of  science,  it  seems 
to  me  that  something  more  than  an  opinion  is  required  as  the 
basis  of  a  far-reaching  theory. f 

*  To  save  space  and  exclude  needless  complication  I  have  omitted  these 
passages  from  the  preceding  divisions  of  this  appendix. 

f  Though  Professor  Weismann  does  not  take  up  the  challenge,  Dr. 
Romanes  does.  He  says : — "  When  selection  is  withdrawn  there  will  be  no 
excessive  plus  variations,  because  so  long  as  selection  was  present  the 
efficiency  of  the  organ  was  maintained  at  its  highest  level :  it  was  only  the 
minus  variations  which  were  then  eliminated"  (Contemporary  Review,  p.  611). 
In  the  first  place,  it  seems  to  me  that  the  phrases  used  in  this  sentence  beg 
the  question.  It  says  that  "  the  efficiency  of  the  organ  was  maintained  at 
its  highest  level "  ;  which  implies  that  the  highest  level  (tacitly  identified  with 
the  greatest  size)  is  the  best  and  that  the  tendency  is  to  fall  below  it.  This 
is  the  very  thing  I  ask  proof  of.  Suppose  I  invert  the  idea  and  say  that 
the  organ  is  maintained  at  its  right  size  by  natural  selection,  because  this 
prevents  increase  beyond  the  size  which  is  best  for  the  organism.  Every 
organ  should  be  in  due  proportion,  and  the  welfare  of  the  creature  as  a  whole 
is  interfered  with  by  excess  as  well  as  by  defect.  It  may  be  directly 
interfered  with — as  for  instance  by  too  big  an  eyelid ;  and  it  may  be  indi- 
rectly interfered  with,  where  the  organ  is  large,  by  needless  weight  and  cost 
of  nutrition.  In  the  second  place  the  question  which  here  concerns  us  is  not 
what  natural  selection  will  do  with  variations.  We  are  concerned  with  the 
previous  question — What  variations  will  arise  ?  An  organ  varies  in  all 
ways ;  and,  unless  reason  to  the  contrary  is  shown,  the  assumption  must  be 
that  variations  in  the  direction  of  increase  are  as  frequent  and  as  great  as 
those  in  the  direction  of  decrease.  Take  the  case  of  the  tongue.  Certainly 
there  are  tongues  inconveniently  large,  and  probably  tongues  inconveniently 
small.  What  reason  have  we  for  assuming  that  the  inconveniently  small 
tongues  occur  more  frequently  than  the  inconveniently  large  ones?  None 
that  I  can  see.  Dr.  Romanes  has  not  shown  that  when  natural  selection 
ceases  to  act  on  an  organ  the  minus  variations  in  each  new  generation  will 
exceed  the  plus  variations.  But  if  they  are  equal  the  alleged  process  of  pan- 
mixia has  no  place. 


668  APPENDIX  B. 

Though  the  counter-opinion  of  one  who  is  not  a  naturalist  (as 
Professor  Weismann  points  out)  may  be  of  relatively  small  value, 
yet  I  must  here  again  give  it,  along  with  a  final  reason  for  it. 
And  this  reason  shall  be  exhibited,  not  in  a  qualitative  form, 
but  in  a  quantitative  form.  Let  us  quantify  the  terms  of  the 
hypothesis  by  weights ;  and  let  us  take  as  our  test  case  the  rudi- 
mentary hind-limbs  of  the  whale.  Zoologists  are  agreed  that 
the  whale  has  been  evolved  from  a  mammal  which  took  to 
aquatic  habits,  and  that  its  disused  hind-limbs  have  gradually 
disappeared.  When  they  ceased  to  be  used  in  swimming,  natural 
selection  played  a  part — probably  an  important  part — in  decreas- 
ing them ;  since,  being  then  impediments  to  movement  through 
the 'water,  they  diminished  the  attainable  speed.  It  may  be,  too, 
that  for  a  period  after  disappearance  of  the  limbs  beneath  the 
skin,  survival  of  the  fittest  had  still  some  effect.  But  during  the 
latter  stages  of  the  process  it  had  no  effect ;  since  the  rudiments 
caused  no  inconvenience  and  entailed  no  appreciable  cost.  Here, 
therefore,  the  cause,  if  Professor  Weismann  is  right,  must  have 
been  panmixia.  Dr.  Struthers,  Professor  of  Anatomy  at  Aber- 
deen, whose  various  publications  show  him  to  be  a  high,  if  not 
the  highest,  authority  on  the  anatomy  of  these  great  cetaceans, 
has  kindly  taken  much  trouble  in  furnishing  me  with  the  need- 
ful data,  based  upon  direct  weighing  and  measuring  and  estima- 
tion of  specific  gravity.  In  the  Black  Whale  (Balcenoptera  borealis) 
there  are  no  rudiments  of  hind-limbs  whatever :  rudiments  of  the 
pelvic  bones  only  remain.  A  sample  of  the  Greenland  Right 
Whale,  estimated  to  weigh  44,800  Ibs.,  had  femurs  weighing 
together  3^  ozs. ;  while  a  sample  of  the  Razor-back  Whale 
(Balcenoptera  musculus),  50  feet  long,  and  estimated  to  weigh 
56,000  Ibs.,  had  rudimentary  femurs  weighing  together  one  ounce  ; 
so  that  these  vanishing  remnants  of  hind-limbs  weighed  but  one- 
896,000th  part  of  the  animal.  Now  in  considering  the  alleged 
degeneration  by  panmixia,  we  have  first  to  ask  why  these  femurs 
must  be  supposed  to  have  varied  in  the  direction  of  decrease 
rather  than  in  the  direction  of  increase.  During  its  evolution 
from  the  original  land-mammal,  the  whale  has  grown  enormously, 
implying  habitual  excess  of  nutrition.  Alike  in  the  embryo  and 
in  the  growing  animal,  there  must  have  been  a  chronic  plethora. 
Why,  then,  should  we  suppose  these  rudiments  to  have  become 
smaller  ?  Why  should  they  not  have  enlarged  by  deposit  in 
them  of  superfluous  materials  ?  But  let  us  grant  the  unwarranted 
assumption  of  predominant  minus  variations.  Let  us  say  that 
the  last  variation  was  a  reduction  of  one-half — that  in  some  in- 
dividuals the  joint  weight  of  the  femurs  was  suddenly  reduced 
from  two  ounces  to  one  ounce — a  reduction  of  one-900,000th  of 
the  creature's  weight.  By  inter-crossing  with  those  inheriting 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      669 

the  variation,  the  reduction,  or  a  part  of  the  reduction,  was  made 
a  trait  of  the  species.  Now,  in  the  first  place,  a  necessary  im- 
plication is  that  this  minus  variation  was  maintained  in  posterity. 
So  far  from  having  reason  to  suppose  this,  we  have  reason  to 
suppose  the  contrary.  As  before  quoted,  Mr.  Darwin  says  that 
"unless  carefully  preserved  by  man,"  "any  particular  varia- 
tion would  generally  be  lost  by  crossing,  reversion,  and  the  acci- 
dental destruction  of  the  varying  individuals."  *  And  Mr.  Galton, 
in  his  essay  on  •'  Regression  towards  Mediocrity,"  f  contends  that 
not  only  do  deviations  of  the  whole  organism  from  the  mean  size 
tend  to  thus  disappear,  but  that  deviations  in  its  components  do 
so.  Hence  the  chances  are  against  such  minus  variation  being  so 
preserved  as  to  affect  the  species  by  panmixia.  In  the  second 
place,  supposing  it  to  be  preserved,  may  we  reasonably  assume 
that,  by  inter-crossing,  this  decrease,  amounting  to  about  a 
millionth  part  of  the  creature's  weight,  will  gradually  affect  the 
constitutions  of  all  Razor-back  Whales  distributed  over  the  Arctic 
seas  and  the  North  Atlantic  Ocean,  from  Greenland  to  the  Equa- 
tor ?  Is  this  a  credible  conclusion  ?  For  three  reasons,  then,  the 
hypothesis  must  be  rejected. 

Thus,  the  only  reasonable  interpretation  is  the  inheritance  of 
acquired  characters.  If  the  effects  of  use  and  disuse,  which  are 
known  causes  of  change  in  each  individual,  influence  succeeding 
individuals — if  functionally-produced  modifications  of  structure 
are  transmissible,  as  well  as  modifications  of  structure  otherwise 
arising — then  this  reduction  of  the  whale's  hind  limbs  to  minute 
rudiments  is  accounted  for.  The  cause  has  been  unceasingly 
operative  on  all  individuals  of  the  species  ever  since  the  trans- 
formation began. 

In  one  case  see  all.  If  this  cause  has  thus  operated  on  the 
limbs  of  the  whale,  it  has  thus  operated  in  all  creatures  on  all 
parts  having  active  functions. 

At  the  outset  I  intimated  that  I  must  limit  my  replies  to 
those  arguments  of  Professor  Weismann  which  are  contained  in 
his  first  article.  That  those  contained  in  his  second  might  be 
dealt  with  no  less  effectually,  did  time  and  space  permit,  is  mani- 
fest to  me;  but  about  the  probability  of  this  the  reader  must 
form  his  own  judgment.  My  replies  thus  far  may  be  summed  up 
as  follows : — 

Professor  Weismann  says  he  has  disproved  the  conclusion  that 
degeneration  of  the  little  toe  has  resulted  from  inheritance  of  ac- 
quired characters.  But  his  reasoning  fails  against  an  interpre- 
tation he  overlooks.  A  profound  modification  of  the  hind  limbs 

*  The  Variation  of  Animal*  and  Plants  under  Domestication,  vol.  ii,  p.  292. 
\  Journal  of  the  Anthropological  Institute  for  1885,  p.  253. 


670  APPENDIX  B, 

and  their  appendages  must  have  taken  place  during  the  transition 
from  arboreal  habits  to  terrestrial  habits ;  and  dwindling  of  the 
little  toe  is  an  obvious  consequence  of  disuse,  at  the  same  time 
that  enlargement  of  the  great  toe  is  an  obvious  consequence  of 
increased  use. 

The  entire  argument  based  on  the  unlike  forms  and  instincts 
presented  by  castes  of  social  insects  is  invalidated  by  an  omission. 
Until  probable  conclusions  are  reached  respecting  the  characters 
which  such  insects  brought  with  them  into  the  organized  social 
state,  no  valid  inferences  can  be  drawn  respecting  characters  de- 
veloped during  that  state. 

A  further  large  error  of  interpretation  is  involved  in  the  as- 
sumption that  the  different  caste-characters  are  transmitted  to 
them  in  the  eggs  laid  by  the  mother  insect.  While  we  have 
evidence  that  the  unlike  structures  of  the  sexes  are  determined  by 
nutrition  of  the  germ  before  egg-laying,  we  have  evidence  that 
the  unlike  structures  of  classes  are  caused  by  unlikenesses  of  nutri- 
tion of  the  larvae.  That  these  varieties  of  forms  do  not  result 
from  varieties  of  germ-plasms,  is  demonstrated  by  the  fact  that 
where  there  are  varieties  of  germ -plasms,  as  in  varieties  of  the 
same  species  of  mammal,  no  deviations  in  feeding  prevent  display 
of  their  structural  results. 

For  such  caste-modifications  as  those  of  the  Amazon-ants, 
which  are  unable  to  feed  themselves,  there  is  a  feasible  explana- 
tion other  than  Professor  Weismann's.  The  relation  of  common 
ants  to  their  domestic  animals — aphides  and  coccids — which  yield 
them  food  on  solicitation,  does  not  differ  widely  from  this  rela- 
tion between  these  Amazon-ants  and  their  domestic  animals — the 
slave-ants.  And  the  habit  of  being  fed,  contracted  during  the 
first  stages  of  their  parasitic  life,  when  there  were  perfect  males 
and  females,  may,  during  that  stage,  have  become  established  by 
inheritance.  Meanwhile  the  opposed  interpretation — that  this  in- 
capacity has  resulted  from  the  selection  of  those  ant-communities 
the  queens  of  which  laid  eggs  that  had  so  varied  as  to  entail  this 
incapacity — implies  that  a  scarcely  appreciable  economy  of  nerve- 
matter  advantaged  the  stirp  so  greatly  as  to  cause  it  to  spread 
more  than  other  stirps :  an  incredible  supposition. 

As  the  outcome  of  these  alternative  interpretations  we  saw 
that  the  argument  respecting  the  co-adaptation  of  co-operative 
parts,  which  Professor  Weismann  thinks  is  furnished  to  him  by 
the  Amazon-ants,  disappears.  The  ancestral  ants  were  conquering 
ants.  These  founded  the  communities ;  and  hence  those  members 
of  the  present  communities  which  are  most  like  them  are  the 
Amazon-ants.  If  so,  the  co-adaptation  of  the  co-operative  parts 
was  effected  by  inheritance  during  the  solitary  and  semi-social 
stages.  Even  were  there  no  such  solution,  the,  opposed,  solution 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.       f,7i 

will  be  unacceptable.  These  simultaneous  appropriate  variations 
of  the  co-operative  parts  in  sizes,  shapes,  and  proportions,  are 
supposed  to  be  effected  by  simultaneous  variations  in  the  "  deter- 
minants "  of  the  germ-plasms ;  and  in  the  absence  of  an  assigned 
physical  cause,  this  implies  a  fortuitous  concourse  of  appropriate 
variations,  which  carries  us  back  to  a  "  fortuitous  concourse  of 
atoms."  This  may  just  as  well  be  extended  to  the  entire  organ- 
ism. The  old  hypothesis  of  special  creations  is  more  consistent 
and  comprehensible. 

To  rebut  my  inference  drawn  from  the  distribution  of  dis- 
criminativeness,  Professor  Weismann  uses  not  an  argument  but 
the  blank  form  of  an  argument.  The  ability  to  discriminate  one 
twenty-fourth  of  an  inch  by  the  tongue-tip  may  have  been  useful 
to  the  ape  :  no  conceivable  use  being  even  suggested.  And  then 
the  great  body  of  my  argument  derived  from  the  distribution  of 
discriminativeness  over  the  skin,  which  amply  suffices,  is  wholly 
ignored. 

The  tacit  challenge  I  gave  to  name  some  facts  in  support  of 
the  hypothesis  of  panmixia — or  even  a  solitary  fact — is  passed 
by.  It  remains  a  pure  speculation  having  no  basis  but  Pro- 
fessor Weismann's  "  opinion."  When  from  the  abstract  statement 
of  it  we  pass  to  a  concrete  test,  in  the  case  of  the  whale,  we 
find  that  it  necessitates  an  unproved  and  improbable  assumption 
respecting  plus  and  minus  variations ;  that  it  ignores  the  unceas- 
ing tendency  to  reversion ;  and  that  it  implies  an  effect  out  of  all 
proportion  to  the  cause. 

It  is  curious  what  entirely  opposite  conclusions  men  may 
draw  from  the  same  evidence.  Professor  Weismann  thinks  he 
has  shown  that  the  "  last  bulwark  of  the  Lamarckian  principle  is 
untenable."  Most  readers  will  hold  with  me  that  he  is,  to  use 
the  mildest  word,  premature  in  so  thinking.  Contrariwise  my 
impression  is  that  he  has  not  shown  either  this  bulwark  or  any 
other  bulwark  to  be  untenable;  but  rather  that  while  his  assault 
has  failed  it  has  furnished  opportunity  for  strengthening  sundry 
of  the  bulwarks. 


IV. 

Among  those  who  follow  a  controversy  to  its  close,  not  one  in 
a  hundred  turns  back  to  its  beginning  to  see  whether  its  chief 
theses  have  been  dealt  with.  Very  often  the  leading  arguments 
of  one  disputant,  seen  by  the  other  to  be  unanswerable,  are  quietly 
ignored,  and  attention  is  concentrated  on  subordinate  arguments 
to  which  replies,  actually  or  seemingly  valid,  can  be  made.  The 
original  issue  is  thus  commonly  lost  sight  of. 


672  APPENDIX  B. 

More  than  once  I  have  pointed  out  that,  as  influencing  men's 
views  about  Education,  Ethics,  Sociology,  and  Politics,  the  ques- 
tion whether  acquired  characters  are  inherited  is  the  most  im- 
portant question  before  the  scientific  world.  Hence  I  cannot 
allow  the  discussion  with  Professor  Weismann  to  end  in  so  futile 
a  way  as  it  will  do  if  no  summary  of  results  is  made.  Here, 
therefore,  I  propose  to  recapitulate  the  whole  case  in  brief.  .Pri- 
marily my  purpose  is  to  "recall  certain  leading  propositions  which, 
having  been  passed  by  unnoticed,  remain  outstanding.  I  will 
turn,  in  the  second  place,  to  such  propositions  as  have  been  dealt 
with ;  hoping  to  show  that  the  replies  given  are  invalid,  and  con- 
sequently that  these  propositions  also  remain  outstanding. 

But  something  beyond  a  summing-up  is  intended.  A  few 
pages  at  the  close  will  be  devoted  to  setting  forth  new  evidence 
which  has  come  to  light  since  the  controversy  commenced — evi- 
dence which  many  will  think  sufficient  in  itself  to  warrant  a  posi- 
tive conclusion. 

The  fact  that  the  tip  of  the  fore  finger  has  thirty  times  the 
power  of  discrimination  possessed  by  the  middle  of  the  back, 
and  that  various  intermediate  degrees  of  discriminative  power 
are  possessed  by  various  parts  of  the  skin,  was  set  down  as  a 
datum  for  my  first  argument.  The  causes  which  might  be  as- 
signed for  these  remarkable  contrasts  were  carefully  examined 
under  all  their  aspects.  I  showed  in  detail  that  the  contrasts 
could  not  in  any  way  be  accounted  for  by  natural  selection.  I 
further  showed  that  no  interpretation  of  them  is  afforded  by  the 
alleged  process  of  panmixia :  this  has  no  locus  standi  in  the  case. 
Having  proved  experimentally,  that  ability  of  the  fingers  to  dis- 
criminate is  increased  by  practice,  and  having  pointed  out  that 
gradations  of  discriminativeness  in  different  parts  correspond  with 
gradations  in  the  activities  of  the  parts  as  used  for  tactual  ex- 
ploration, I  argued  that  these  contrasts  have  arisen  from  the 
organized  and  inherited  effects  of  tactual  converse  with  surround- 
ing things,  varying  in  its  degrees  according  to  the  positions  of 
the  parts — in  other  words,  that  they  are  due  to  the  inheritance 
of  acquired  characters.  As  a  crowning  proof  I  instanced  the  case 
of  the  tongue-tip,  which  has  twice  the  discriminativeness  of  the 
forefinger-tip :  pointing  out  that  consciously,  or  semi-consciously, 
or  unconsciously,  the  tongue-tip  is  perpetually  exploring  the  inner 
surfaces  of  the  teeth. 

Singling  out  this  last  case,  Professor  Weismann  made,  or 
rather  adopted  from  Dr.  Romanes,  what  professed  to  be  a  reply 
but  was  nothing  more  than  the  blank  form  of  a  reply.  It  was 
said  that  though  this  extreme  discriminativeness  of  the  tongue- 
tip  is  of  no  use  to  mankind,  it  may  have  been  of  use  to  certain 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.       073 

ancestral  primates.  No  evidence  of  any  such  use  was  given  ;  no 
imaginable  use  was  assigned.  It  was  simply  suggested  that  there 
perhaps  was  a  use. 

In  my  rejoinder,  after  indicating  the  illusory  nature  of  this 
proceeding  (which  is  much  like  offering  a  cheque  on  a  bank 
whore  no  assets  have  been  deposited  to  meet  it),  I  pointed  out 
that  had  the  evidence  furnished  by  the  tongue  tip  never  been 
mentioned,  the  evidence  otherwise  furnished  amply  sufficed.  I 
then  drew  attention  to  the  fact  that  this  evidence  had  been  passed 
over,  and  tacitly  inquired  why. 

No  reply.* 

In  his  essay  on  a  The  All-Sufficiency  of  Natural  Selection," 
Professor  Weismann  set  out,  not  by  answering  one  of  the  argu- 
ments I  had  used,  but  by  importing  into  the  discussion  an  argu- 
ment used  by  another  writer,  which  it  was  easy  to  meet.  It  had 
been  contended  that  the  smallness  and  deformity  of  the  little  toe 
are  consequent  upon  the  effects  of  boot-pressure,  inherited  from 
generation  to  generation.  To  this  Professor  Weismann  made  the 
sufficient  reply  that  the  fusion  of  the  phalanges  and  otherwise 
degraded  structure  of  the  little  toe,  exist  among  peoples  who  go 
barefoot. 

In  my  "  Rejoinder  "  I  said  that  though  the  inheritance  of  ac- 
quired characters  does  not  explain  this  degradation  in  the  way 
alleged,  it  explains  it  in  a  way  which  Professor  Weismann  over- 
looks. The  cause  is  one  which  has  been  operating  ever  since  the 
earliest  anthropoid  creatures  began  to  decrease  their  life  in  trees 
and  increase  their  life  on  the  earth's  surface.  The  mechanics  of 
walking  and  running,  in  so  far  as  they  concern  the  question  at 
issue,  were  analyzed ;  and  it  was  shown  that  effort  is  economized 
and  efficiency  increased  in  proportion  as  the  stress  is  thrown 
more  and  more  on  the  inner  digits  of  the  foot  and  less  and  less 
on  the  outer  digits.  So  that  thus  the  foot  furnishes  us  simul- 
taneously with  an  instance  of  increase  from  use  and  of  decrease 
from  disuse  ;  a  further  disproof  being  yielded  of  the  allegation 
that  co-operative  parts  vary  together,  since  we  have  here  co-opera- 
tive parts  of  which  one  grows  while  the  other  dwindles. 

I  ended  by  pointing  out  that,  so  far  from  strengthening  his 
own  case,  Professor  Weismann  had,  by  bringing  into  the  contro- 

*  In  "The  All-Sufficiency  of  Natural  Selection "  (Contemporary  Review, 
Sept.,  1893,  p.  311),  Professor  Weismann  writes :— "I  have  ever  contended 
that  the  acceptance  of  a  principle  of  explanation  is  justified,  if  it  can  be 
shown  that  without  it  certain  facts  are  inexplicable."  Unless,  then,  Prof. 
Weismann  can  show  that  the  distribution  of  discriminativeness  is  otherwise 
explicable,  he  is  bound  to  accept  the  explanation  I  have  given,  and  admit  tl.o 
inheritance  of  acquired  characters. 


074  APPENDIX   B. 

versy  this   changed   structure   of    the    foot,   given   occasion    for 
strengthening  the  opposite  case. 
No  reply. 

We  come  now  to  Professor  Weismann's  endeavour  to  disprove 
my  second  thesis — that  it  is  impossible  to  explain  by  natural 
selection  alone  the  co-adaptation  of  co-operative  parts.  It  is 
thirty  years  since  this  was  set  forth  in  The  Principles  of  Biology. 
In  §  166  I  instanced  the  enormous  horns  of  the  extinct  Irish  elk, 
and  contended  that  in  this,  and  in  kindred  cases,  where  for  the 
efficient  use  of  some  one  enlarged  part  many  other  parts  have  to 
be  simultaneously  enlarged,  it  is  out  of  the  question  to  suppose 
that  they  can  have  all  spontaneously  varied  in  the  required  pro- 
portions. In  "  The  Factors  of  Organic  Evolution,"  by  way  of 
enforcing  this  argument,  which  had,  so  far  as  I  know,  never  been 
met,  I  dwelt  upon  the  aberrant  structure  of  the  giraffe.  And 
then,  in  the  essay  which  initiated  this  controversy,  I  brought 
forward  yet  a  third  case — that  of  an  animal  which,  previously 
accustomed  only  to  walking,  acquires  the  power  of  leaping. 

In  the  first  of  his  articles  in  the  Contemporary  Review  (Sep- 
tember, 1893),  Professor  Weismann  made  no  direct  reply,  but  he 
made  an  indirect  reply.  He  did  not  attempt  to  show  how  there 
could  have  taken  place  in  the  stag  the  "  harmonious  variation  of 
the  different  parts  that  co-operate  to  produce  one  physiological 
result"  (p.  311) ;  but  he  contended  that  such  harmonious  varia- 
tion must  have  taken  place,  because  the  like  has  taken  place  in 
"the  neuters  of  state-forming  insects" — ''animal  forms  which  do 
not  reproduce  themselves,  but  are  always  propagated  anew  by 
parents  which  are  unlike  them"  (p.  313),  and  which  therefore 
cannot  have  transmitted  acquired  characters.  Singling  out  those 
soldier-neuters  which  exist  among  certain  kinds  of  ants,  he  de- 
scribed (p.  318)  the  many  co-ordinated  parts  required  to  make 
their  fighting  organs  efficient.  He  then  argued  that  the  required 
simultaneous  changes  can  "  only  have  arisen  by  a  selection  of  the 
parent-ants  dependent  on  the  fact  that  those  parents  which  pro- 
duced the  best  workers  had  always  the  best  prospect  of  the  per- 
sistence of  their  colony.  No  other  explanation  is  conceivable;  and 
it  is  just  because  no  other  explanation  is  conceivable,  that  it  is  neces- 
sary for  UK  to  accept  the  principle  of  natural  selection"  (pp.  318-9). 

[This  passage  initiated  a  collateral  controversy,  which,  as  con- 
tinually happens,  has  greatly  obscured  the  primary  controversy. 
It  became  a  question  whether  these  forms  of  neuter  insects  have 
arisen  as  Professor  Weismann  assumes,  or  whether  they  have 
arisen  from  arrested  development  consequent  upon  innutrition. 
To  avoid  entanglements  I  must  for  the  present  pass  over  this  col- 


INADEQUACY  OF  NATURAL  SELECTION,  ETC.      675 

lateral  controversy,  intending  to  resume  it  presently,  when  the 
original  issues  have  been  dealt  with.] 

No  one  will  suspect  me  of  thinking  that  the  inconceivability 
of  the  negation  is  not  a  valid  criterion,  since,  in  "  The  Universal 
Postulate,"  published  in  the  Westminster  Review  in  1852  and 
afterwards  in  The  Principles  of  Psychology,  I  contended  that  it  is 
the  ultimate  test  of  truth.  But  then  in  every  case  there  has  to 
be  determined  the  question — Is  the  negation  inconceivable ;  and 
in  assuming  that  it  is  so  in  the  case  named,  lies  the  fallacy  of  the 
above-quoted  passage.  The  three  separate  ways  in  which  I  dealt 
with  this  position  of  Professor  Weismann  are  as  follows : — 

If  we  admit  the  assumption  that  the  form  of  the  soldier-ant 
has  been  developed  since  the  establishment  of  the  organized  ant- 
community  in  which  it  exists,  Professor  Weismann's  assertion 
that  no  other  process  than  that  which  he  alleges  is  conceivable, 
is  true.  But  I  pointed  out  that  this  assumption  is  inadmissible ; 
and  that  no  valid  conclusion  respecting  the  genesis  of  the  soldier- 
ant  can  be  drawn  without  postulating  either  the  ascertained,  or 
the  probable,  structure  of  those  pre-social,  or  semi-social,  ants 
from  which  the  organized  social  ants  have  descended.  I  went  on 
to  contend  that  the  pre-social  type  must  have  been  a  conquering 
type,  and  that  therefore  in  all  probability  the  soldier-ants  repre- 
sent most  nearly  the  structures  of  those  ancestral  ants  which  ex- 
isted when  the  society  had  perfect  males  and  females  and  could 
transmit  acquired  characters,  while  the  other  members  of  the 
existing  communities  are  degraded  forms  of  the  type. 

No  reply. 

A  further  argument  I  used  was  that  where  there  exist  differ- 
ent castes  among  the  neuter-ants,  as  those  seen  in  the  soldiers  and 
workers  of  the  Driver  ants  of  West  Africa,  "  they  graduate  in- 
sensibly into  each  other  "  alike  in  their  sizes  and  in  their  struc- 
tures ;  and  that  Professor  Weismann's  hypothesis  implies  a  spe- 
cial set  of  "  determinants  "  for  each  intermediate  form.  Or  if  he 
should  say  that  the  intermediate  forms  result  from  mixtures  of 
the  determinants  of  the  two  extreme  forms,  there  still  remains 
the  further  difficulty  that  natural  selection  has  maintained,  for 
innumerable  generations,  these  intermediate  forms  which  are  in- 
jurious deviations  from  the  useful  extreme  forms. 

No  reply. 

One  further  reason — fatal  it  seems  to  me — was  urged  in  bar 
of  his  interpretation.  No  physical  cause  has  bee.n,  or  can  be, 
assigned,  why  in  the  germ-plasm  of  any  particular  queen-ant,  the 
"  determinants "  initiating  these  various  co-operative  organs,  all 
simultaneously  vary  in  fitting  ways  and  degrees,  and  still  less 
why  there  occur  such  co-ordinated  variations  generation  after 
generation,  until  by  their  accumulated  results  these  efficient  no- 


676  APPENDIX  B. 

operative  structures  have  been  evolved.  I  pointed  out  that  in 
the  absence  of  any  assigned  or  assignable  physical  cause,  it  is 
necessary  to  assume  a  fortuitous  concurrence  of  favourable  varia- 
tions, which  means  "  a  fortuitous  concourse  of  atoms ;  "  and  that 
it  would  be  just  as  rational,  and  much  more  consistent,  to  assume 
that  the  structure  of  the  entire  organism  thus  resulted. 
No  reply. 

It  is  reasonable  to  suspect  that  Professor  Weismann  recog- 
nized these  difficulties  as  insuperable,  for,  in  his  Romanes  Lecture 
on  "  The  Effect  of  External  Influences  upon  Development,"  instead 
of  his  previous  indirect  reply,  he  makes  a  direct  reply.  Reverting 
to  the  stag  and  its  enlarging  horns,  he  alleges  a  process  by  which, 
as  he  thinks,  we  may  understand  how,  by  variation  and  selection, 
all  the  bones  and  muscles  of  the  neck,  of  the  thorax,  and  of  the 
fore-legs,  are  step  by  step  adjusted  in  their  sizes  to  the  increasing 
sizes  of  the  horns.  He  ascribes  this  harmonization  to  the  inter- 
nal struggle  for  nutriment,  and  that  survival  of  the  fittest  which 
takes  place  among  the  parts  of  an  organism :  a  process  which  he 
calls  u  intra-individual-selQCtioTH,  or  more  briefly — intra- selection  " 
(p.  12) 

"  Wilhclm  Roux  has  given  an  explanation  of  the  cause  of  these  wonder- 
fully fine  adaptations  by  applying  the  principle  of  selection  to  the  parts  of  the 
organism.  Just  as  there  is  a  struggle  for  survival  among  the  individuals  of 
a  species,  and  the  fittest  are  victorious,  so  also  do  even  the  smallest  living 
particles  contend  with  one  another,  and  those  that  succeed  best  in  securing 
food  and  place  grow  and  multiply  rapidly,  and  so  displace  those  that  are  less 
suitably  equipped  "  (p.  12).* 

That  I  do  not  explain  as  he  does  the  co-adaptation  of  co- 
operative parts,  Professor  Weismann  ascribes  to  my  having  over- 
looked this  "principle  of  intra  selection " — an  unlucky  supposi- 
tion, as  we  see.  But  I  do  not  think  that  when  recognizing  it  a 
generation  ago,  I  should  have  seen  its  relevancy  to  the  question 

*  Prof.  Weismann  is  unaware  that  the  view  here  ascribed  to  Roux,  writing 
in  1881,  is  of  far  earlier  date.  In  the  Westminster  Review  for  January,  1860, 
in  an  essay  on  "  The  Social  Organism,"  I  wrote : — "  One  more  parallelism  to 
be'  here  noted,  is  that  the  different  parts  of  a  social  organism,  like  the  differ- 
ent parts  of  an  individual  organism,  compete  for  nutriment ;  and  severally 
obtain  more  or  less  of  it  according  as  they  are  discharging  more  or  less  duty." 
(See  also  Essays,  i,  290.)  And  then,  in  1876,  in  TJie  Principles  of  Sociology, 
vol.  i,  §  247,  I  amplified  the  statement  thus : — "  All  other  organs,  therefore, 
jointly  and  individually,  compete  for  blood  with  each  organ  .  .  .  local 
tissue-formation  (which  under  normal  conditions  measures  the  waste  of  tissue 
in  discharging  function)  is  itself  a  cause  of  increased  supply  of  materials 
the  resulting  competition,  not  between  units  simply,  but  between  organs, 
causes  in  a  society,  as  in  a  living  body,  high  nutrition  and  growth  of  part* 
called  into  greatest  activity  by  the  requirements  of  the  rest."  Though  I  did 
not  use  the  imposing  phrase  "  intra-individual-selection,"  the  process  described 
is  the  same. 


INADEQUACY  OP  NATURAL  SELECTION,   ETC.       677 

at  issue,  had  that  issue  then  been  raised,  and  I  certainly  do  not 
see  it  now.  Full  reproduction  of  Professor  Weismann's  explana- 
tion is  impracticable,  for  it  occupies  several  pages,  but  here  are 
the  essential  sentences  from  it : — 

"  The  great  significance  of  mtra-selection  appears  to  me  not  to  depend  on 
its  producing  structures  that  are  directly  transmissible, — it  cannot  do  that, — 
but  rather  consists  in  its  causing  a  development  of  the  germ-structure, 
;ic([uired  by  the  selection  of  individuals,  which  will  be  suitable  to  varying 
c  editions.  .  .  .  We  may  therefore  say  that  intra-selection  effects  tho 
adaptation  of  the  individual  to  its  chance  developmental  conditions, — the 
suiting  of  the  hereditary  primary  constituents  to  fresh  circumstances" 
(p.  16).  .  .  .  "But  as  the  primary  variations  in  the  phyletic  metamor- 
phosis occurred  little  by  little,  the  secondary  adaptations  would  probably  as 
a  rule  be  able  to  keep  pace  with  them.  Time  would  thus  be  gained  till,  in 
the  course  of  generations,  by  constant  selection  of  those  germs  the  primary 
constituents  of  which  are  best  suited  to  one  another,  the  greatest  possible 
degree  of  harmony  may  be  reached,  and  consequently  a  definitive  metamor- 
phosis of  the  species  involving  all  the  parts  of  the  individual  may  occur " 
(p.  19). 

The  connecting  sentences,  along  with  those  which  precede 
and  succeed,  would  not,  if  quoted,  give  to  the  reader  clearer 
conceptions  than  these  by  themselves  give.  But  when  dis- 
entangled from  Professor  Weismann's  involved  statements,  the 
essential  issues  are,  I  think,  clear  enough.  In  the  case  of  the 
stag,  that  daily  working  together  of  the  numerous  nerves,  muscles, 
and  bones  concerned,  by  which  they  are  adjusted  to  the  carrying 
and  using  of  somewhat  heavier  horns,  produces  on  them  effects 
which,  as  I  hold,  are  inheritable,  but  which,  as  Professor  Weis- 
mann  holds,  are  not  inheritable.  If  they  are  not  inheritable, 
what  must  happen  ?  A  fawn  of  the  next  generation  is  born  with 
no  such  adjustment  of  nerves,  muscles  and  bones  as  had  been 
produced  by  greater  exercise  in  the  parent,  and  with  no  tendency 
to  such  adjustment.  Consequently  if,  in  successive  generations, 
the  horns  go  on  enlarging,  all  these  nerves,  muscles,  and  bones, 
remaining  of  the  original  sizes,  become  utterly  inadequate.  The 
result  is  loss  of  life :  the  process  of  adaptation  fails.  "  No,"  says 
Professor  Weismann,  "we  must  conclude  that  the  germ-plasm 
has  varied  in  the  needful  manner."  How  so  ?  The  process  of 
"  intra-individual  selection,"  as  he  calls  it,  can  have  had  no  effect, 
since  the  cells  of  the  soma  cannot  influence  the  reproductive  cells. 
In  what  way,  then,  has  the  germ-plasm  gained  the  characters 
required  for  producing  simultaneously  all  these  modified  co- 
operative parts.  Well,  Professor  Weismann  tells  us  merely  that 
we  must  suppose  that  the  germ-plasm  acquires  a  certain  sensitive- 
ness such  as  gives  it  a  proclivity  to  development  in  the  requisite 
ways.  How  is  such  proclivity  obtainable  ?  Only  by  having  a 
multitude  of  its  "  determinants "  simultaneously  changed  in  fit 
modes.  Emphasizing  the  fact  that  even  a  small  failure  in  any 
44 


(578  APPENDIX  B. 

one  of  the  co-operative  parts  may  be  fatal,  as  the  sprain  of  an 
over-taxed  muscle  shows  us,  I  alleged  that  the  chances  are  infinity 
to  one  against  the  needful  variations  taking  place  at  the  same 
time.  Divested  of  its  elaboration,  its  abstract  words  and  tech- 
nical phrases,  the  outcome  of  Professor  Weismann's  explanation 
is  that  he  accepts  this,  and  asserts  that  the  infinitely  improbable 
thing  takes  place ! 

Either  his  argument  is  a  disguised  admission  of  the  inheritable- 
ness  of  acquired  characters  (the  effects  of  "  intra-selection  ")  or 
else  it  is,  as  before,  the  assumption  of  a  fortuitous  concourse  of 
favourable  variations  in  the  determinants — "  a  fortuitous  con- 
course of  atoms." 

Leaving  here  this  main  issue,  I  return  now  to  that  collateral 
issue  named  on  a  preceding  page  as  being  postponed — whether 
the  neuters  among  social  insects  result  from  specially  modified 
germ-plasms  or  whether  they  result  from  the  treatment  received 
during  their  larval  stages. 

For  the  substantiation  of  his  doctrine  Professor  Weismann  is 
obliged  to  adopt  the  first  of  these  alternatives ;  and  in  his 
Romanes  Lecture  he  found  it  needful  to  deal  with  the  evidence 
I  brought  in  support  of  the  second  alternative.  He  says  that 
"  poor  feeding  is  not  the  causa  efficients  of  sterility  among  bees, 
but  is  merely  the  stimulus  which  not  only  results  in  the  formation 
of  rudimentary  ovaries,  but  at  the  same  time  calls  forth  all  the  other 
distinctive  characters  of  the  workers "  (pp.  29-30) ;  and  he  says 
this  although  he  has  in  preceding  lines  admitted  that  it  is  "  true 
of  all  animals  that  they  reproduce  only  feebly  or  not  at  all  when 
badly  and  insufficiently  nourished : "  a  known  cause  being  thus 
displaced  by  a  supposed  cause.  But  Professor  Weismann  pro- 
ceeds to  justify  his  interpretation  by  experimentally-obtained 
evidence. 

He  "  reared  large  numbers  of  the  eggs  of  a  female  blow-fly  " ; 
the  larvaB  of  some  he  fed  abundantly,  but  the  larvae  of  others 
sparingly ;  and  eventually  he  obtained  from  the  one  set  flies  of 
full  size,  and  from  the  other  small  flies.  Nevertheless  the  small 
flies  were  fertile,  as  well  as  the  others.  Here,  then,  was  proof 
that  innutrition  had  not  produced  infertility ;  and  he  contends 
that  therefore  among  the  neuter  social  insects,  infertility  has  not 
resulted  from  innutrition.  The  argument  seems  strong,  and  to 
many  will  appear  conclusive  ;  but  there  are  two  differences  which 
entirely  vitiate  the  comparison  Professor  Weismann  institutes. 

One  of  them  has  been  pointed  out  by  Mr.  Cunningham.  In 
the  case  of  the  blow-fly  the  food  supplied  to  the  larvae  though 
different  in  quantity  was  the  same  in  quality ;  in  the  case  of  the 
social  insects  the  food  supplied,  whether  or  not  different  in 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.       679 

quantity,  differs  in  quality.  Among  bees,  wasps,  ants,  &c.,  the 
larvae  of  the  reproductive  forms  are  fed  upon  a  more  nitrogenous 
food  than  are  the  larvae  of  the  workers  ;  whereas  the  two  sets  of 
larvae  of  the  blow-fly,  as  fed  by  Professor  Weismann,  were  alike 
supplied  with  highly  nitrogenous  food..  Hence  there  did  not 
exist  the  same  cause  for  non-development  of  the  reproductive 
organs.  Here,  then,  is  one  vitiation  of  the  supposed  parallel. 
There  is  a  second. 

While  the  development  of  an  embryo  follows  in  a  rude  way 
the  phyletic  metamorphoses  passed  through  by  its  ancestry,  the 
order  of  development  of  organs  is  often  gradually  modified  by 
the  needs  of  particular  species  :  the  structures  being  developed 
in  such  order  as  conduces  to  self-sustentation  and  the  welfare  of 
offspring.  Among  other  results  there  arise  differences  in  the 
relative  dates  of  maturity  of  the  reproductive  system  and  of  the 
other  systems.  It  is  clear,  a  priori,  that  it  must  be  fatal  to  a 
species  if  offspring  are  habitually  produced  before  the  conditions 
requisite  for  their  survival  are  fulfilled.  And  hence,  if  the  life 
is  a  complex  one,  and  the  care  taken  of  offspring  is  great,  repro- 
duction must  be  much  longer  delayed  than  where  the  life  is  simple 
and  the  care  of  offspring  absent  or  easy.  The  contrast  between 
men  and  oxen  sufficiently  illustrates  this  truth.  Now  the  sub- 
ordination of  the  order  of  development  of  parts  to  the  needs  of 
the  species,  is  conspicuously  shown  in  the  contrast  between  these 
two  kinds  of  insects  which  Professor  Weismann  compares  as 
though  their  requirements  were  similar.  What  happens  with  the 
blow  fly  ?  If  it  is  able  to  suck  up  some  nutriment,  to  fly  toler- 
ably, and  to  scent  out  dead  flesh,  various  of  its  minor  organs 
may  be  more  or  less  imperfect  without  appreciable  detriment  to 
the  species  :  the  eggs  can  be  laid  in  a  fit  place,  and  that  is  all 
that  is  wanted.  Hence  it  profits  the  species  to  have  the  repro- 
ductive system  developed  comparatively  early — in  advance,  even, 
of  various  less  essential  parts.  Quite  otherwise  is  it  with  social 
insects,  which  take  such  remarkable  care  of  their  young ;  or 
rather  to  make  the  case  parallel — quite  otherwise  is  it  with  those 
types  from  which  the  social  insects  have  descended,  bringing  into 
the  social  state  their  inherited  instincts  and  constitutions.  Con- 
sider the  doings  of  the  mason-wasp,  or  mason-bee,  or  those  of  the 
carpenter-bee.  What,  in  these  cases,  must  the  female  do  that  she 
may  rear  members  of  the  next  gemeration  ?  There  is  a  fit  place 
for  building  or  burrowing  to  be  chosen ;  there  is  the  collecting 
together  of  grains  of  sand  and  cementing  them  into  a  strong  and 
water-proof  cell,  or  there  is  the  burrowing  into  wood  and  there 
building  several  cells ;  there  is  the  collecting  of  food  to  place 
along  with  the  eggs  deposited  in  these  cells,  solitary  or  associated, 
including  that  intelligent  choice  of  small  caterpillars  which,  dis- 


680  APPENDIX  B. 

covered  and  carried  home,  are  carefully  packed  away  and  hypno- 
tized by  a  sting,  so  that  they  may  live  until  the  growing  larva 
has  need  of  them.  For  all  these  proceedings  there  have  to  be 
provided  the  fit  external  organs — cutting  instruments,  <fcc.,  and 
the  fit  internal  organs — complicated  nerve-centres  in  which  are 
located  these  various  remarkable  instincts,  and  ganglia  by  which 
these  delicate  operations  have  to  be  guided.  And  these  special 
structures  have,  some  if  not  all  of  them,  to  be  made  perfect  and 
brought  into  efficient  action  before  egg-laying  takes  place.  Ask 
what  would  happen  if  the  reproductive  system  were  active  in 
advance  of  these  ancillary  appliances.  The  eggs  would  have  to 
be  laid  without  protection  or  food,  and  the  species  would  forth- 
with disappear.  And  if  that  full  development  of  the  reproduc- 
tive organs  which  is  marked  by  their  activity,  is  not  needful  until 
these  ancillary  organs  have  come  into  play,  the  implication,  in 
conformity  with  the  general  law  above  indicated,  is  that  the  per- 
fect development  of  the  reproductive  organs  will  take  place  later 
than  that  of  these  ancillary  organs,  and  that  if  innutrition  checks 
the  general  development,  the  reproductive  organs  will  be  those 
which  chiefly  suffer.  Hence,  in  the  social  types  which  have 
descended  from  these  solitary  types,  this  order  of  evolution  of 
parts  will  be  inherited,  and  will  entail  the  results  I  have  inferred. 

If  only  deductively  reached,  this  conclusion  would,  I  think,  be 
fully  justified.  But  now  observe  that  it  is  more  than  deductively 
reached.  It  is  established  by  observation.  Professor  Riley, 
Ph.D.,  late  Government  Entomologist  of  the  United  States,  in 
his  annual  address  as  President  of  the  Biological  Society  of  Wash- 
ington,* on  January  29,  1894,  said  : — 

"  Among  the  more  curious  facts  connected  with  these  Termites,  because  of 
their  exceptional  nature,  is  the  late  development  of  the  internal  sexual  organs 
in  the  reproductive  forms."  (p.  34.) 

Though  what  has  been  shown  of  the  Termites  has  not  been 
shown  of  the  other  social  insects,  which  belong  to  a  different 
order,  yet,  considering  the  analogies  between  their  social  states 
and  between  their  constitutional  requirements,  it  is  a  fair  infer- 
ence that  what  holds  in  the  one  case  holds  partially,  if  not  fully, 
in  the  other.  Should  it  be  said  that  the  larval  forms  do  not  pass 
into  the  pupa  state  in  the  one  case  as  they  do  in  the  other,  the 
answer  is  that  this  does  not  affect  the  principle.  The  larva 
carries  into  the  pupa  state  a  fixed  quantity  of  tissue-forming 
material  for  the  production  of  the  imago.  If  the  material  is 
sufficient,  then  a  complete  imago  is  formed.  If  it  is  not  sufficient, 
then,  while  the  earlier  formed  organs  are  not  affected  by  the 
deficiency,  the  deficiency  is  felt  when  the  latest  formed  organs 
come  to  be  developed,  and  they  are  consequently  imperfect. 
*  Proceedings  of  the  Biological  Society  of  Washington,  vol.  ix. 


INADEQUACY  OP  NATURAL  SELECTION,   ETC.      681 

Even  if  left  without  reply,  Professor  Weismann's  interpreta- 
tion commits  him  to  some  insuperable  difficulties,  which  I  must 
now  point  out.  Unquestionably  he  has  "  the  courage  of  his 
opinions  ;  "  and  it  is  shown  throughout  this  collateral  discussion 
as  elsewhere.  He  is  compelled  by  accumulated  evidence  to  admit 
"  that  there  is  only  one  kind  of  egg  from  which  queens  and 
workers  as  well  as  males  arise."  *  But  if  the  production  of  one 
or  other  form  from  the  same  germ  does  not  result  from  speciality 
of  feeding,  what  does  it  result  from  ?  Here  is  his  reply : — 

"  We  must  rather  suppose  that  the  primary  constituents  of  two  distinct 
reproductive  systems — e.g.  those  of  the  queen  and  worker — are  contained  in 
the  germ-plasm  of  the  egg."  f 

"  The  courage  of  his  opinions,"  which  Professor  Weismann 
shows  in  this  assumption,  is,  however,  quite  insufficient.  For 
since  he  himself  has  just  admitted  that  there  is  only  one  kind  of 
egg  for  queens,  workers,  and  males,  he  must  at  any  rate  assume 
three  sets  of  "  determinants."  (I  find  that  on  a  subsequent  page 
he  does  so.)  But  this  is  not  enough,  for  there  are,  in  many 
cases,  two  if  not  more  kinds  of  workers,  which  implies  that  four 
sets  of  determinants  must  co-exist  in  the  same  egg.  Even  now 
we  have  not  got  to  the  extent  of  the  assumption  required.  In 
the  address  above  referred  to  on  u  Social  Insects  from  Psychical 
and  Evolutional  Points  of  View,"  Professor  Riley  gives  us  (p.  33) 
the — 

Forms  in  a  Termcs  Colony  under  Normal  Conditions. 
1.  Youngest  larvae. 


2.  Larvae  [of  those]  unfit 
for  reproduction. 

3.  Larvaa  [that  will  be]  fit 
for  reproduction. 

8.  Nymphs  of  1st      9.  Nymphs  of  2nd 
form.                           form. 

10.  Winged  forms. 
11.  True  royal  pairs. 

4.  Larvae  of 
workers. 
I 
6.  Workers. 

6.  Larvae  of 
soldiers. 

7.  Soldiers. 

Hence  as,  in  this  family  tree,  the  royal  pair  includes  male  and 
female,  it  results  that  there  are  jive  different  adult  forms  (Grassi 
says  there  are  two  others)  arising  from  like  eggs  or  larvse  ;  and 
Professor  Weismann's  hypothesis  becomes  proportionately  com- 
plicated. Let  us  observe  what  the  complications  are. 

It  often  happens  in  controversy — metaphysical  controversy 
more  than  any  other — that  propositions  are  accepted  without 
their  terms  having  been  mentally  represented.  In  public  pro- 
ceedings documents  are  often  "  taken  as  read,"  sometimes  with 
mischievous  results ;  and  in  discussions  propositions  are  often 
*  Romanes  Lecture,  p.  29.  f  Jhid.,  p.  35. 


682  APPENDIX  B. 

taken  as  thought  when  they  have  not  been  thought  and  cannot 
be  thought.  It  sufficiently  taxes  imagination  to  assume,  as  Pro- 
fessor Weismann  does,  that  two  sets  of  "  ids  "  or  of  "  determi- 
nants "  in  the  same  egg  are,  throughout  all  the  cell-divisions 
which  end  in  the  formation  of  the  morula,  kept  separate,  so  that 
they  may' subsequently  energize  independently;  or  that  if  they 
are  not  thus  kept  separate,  they  have  the  power  of  segregating  in 
the  required  ways.  But  what  are  we  to  say  when  .three,  four, 
and  even  five  sets  of  "  ids  "  or  bundles  of  "  determinants  "  are 
present  ?  How  is  dichotomous  division  to  keep  these  sets  dis- 
tinct ;  or  if  they  are  not  kept  distinct,  what  shall  we  say  to  the 
chaos  which  must  arise  after  many  fissions,  when  each  set  in  con- 
flict with  the  others  strives  to  produce  its  particular  structure  ? 
And  how  are  the  conquering  determinants  to  find  they  ways  out 
of  the  melee  to  the  places  where  they  are  to  fulfil  their  organizing 
functions  ?  Even  were  they  all  intelligent  beings  and  each  had 
a  map  by  which  to  guide  his  movements,  the  problem  would  be 
sufficiently  puzzling.  Can  we  assume  it  to  be  solved  by  uncon- 
scious units  ? 

Thus  even  had  Professor  Weismann  shown  that  the  special 
structures  of  the  different  individuals  in  an  insect-community  are 
not  due  to  differences  in  the  nurtures  they  receive,  which  he  has 
failed  to  do,  he  would  still  be  met  by  this  difficulty  in  the  way  of 
his  own  view,  in  addition  to  the  three  other  insuperable  difficul- 
ties grouped  together  in  a  preceding  section. 

The  collateral  issue,  which  has  occupied  the  largest  space  in 
the  controversy,  has,  as  commonly  happens,  begotten  a  second 
generation  of  collateral  issues.  Some  of  these  are  embodied  in 
the  form  of  questions  put  to  me,  which  I  must  here  answer,  lest 
it  should  be  supposed  that  they  are  unanswerable  and  my  view 
therefore  untenable. 

In  the  notes  he  appends  to  his  Romanes  Lecture,  Professor 
Weismann  writes  : — 

"One  of  the  questions  put  to  Spencer  by  Ball  is  quite  sufficient  to  show 
the  utter  weakness  of  the  position  of  Lamarckism : — if  their  characteristics 
did  not  arise  among  the  workers  themselves,  but  were  transmitted  from  the 
pre-social  time,  how  does  it  happen  that  the  queens  and  drones  of  every 
generation  can  give  anew  to  the  workers  the  characteristics  which  they  them- 
selves have  long  ago  lost  ?  "  (p.  68). 

It  is  curious  to  see  put  forward  in  so  triumphant  a  manner,  by 
a  professed  naturalist,  a  question  so  easily  disposed  of.  I  answer 
it  by  putting  another.  How  does  it  happen  that  among  those 
moths  of  which  the  female  has  but  rudimentary  wings,  she  con- 
tinues .to  endow  the  males  of  her  species  with  wings  ?  How  docs 
it  happen,  for  example,  that  among  the  Geometridce,  the  peculiar 


INADEQUACY  OP  NATURAL  SELECTION,  ETC.       683 

structures  and  habits  of  which  show  that  they  have  all  descended 
from  a  common  ancestor,  some  species  have  winged  females  and 
some  wingless  females ;  and  that  though  they  have  lost  the  wings 
the  ancestral  females  had,  these  wingless  females  convey  to  the 
males  the  normal  developments  of  wings  ?  Or,  still  better,  how 
is  it  that  in  the  Psychidce  there  are  apterous  worm-like  females, 
which  lay  eggs  that  bring  forth  winged  males  of  the  ordinary 
imago  form  ?  If  for  males  we  read  workers,  the  case  is  parallel 
to  the  cases  of  those  social  insects,  the  queens  of  which  bequeath 
characteristics  they  have  themselves  lost.  The  ordinary  facts  of 
embryonic  evolution  yield  us  analogies.  What  is  the  most  com- 
mon trait  in  the  development  of  the  sexes  ?  When  the  sexual 
organs  of  either  become  pronounced,  the  incipient  ancillary  organs 
belonging  to  the  opposite  sex  cease  to  develop  and  remain  rudi- 
ments, while  the  organs  special  to  the  sex,  essential  and  non- 
essential,  become  fully  developed.  What,  then,  must  happen 
with  the  queen-ant,  which,  through  countless  generations,  has 
ceased  to  use  certain  structures  and  has  lost  them  from  disuse  ? 
If  one  of  the  eggs  which  she  lays,  capable,  as  Professor  Weis- 
mann  admits,  of  becoming  queen,  male,  or  worker  of  one  or  other 
kind,  does  not  at  a  certain  stage  begin  actively  to  develop  its  re- 
productive system,  then  those  organs  of  the  ancestral  or  pre-social 
type  which  the  queen  has  lost  begin  to  develop,  and  a  worker 
results. 

Another  difficulty  in  the  way  of  my  view,  supposed  to  be  fatal, 
is  that  presented  by  the  Honey-ants — aberrant  members  of  certain 
ant-colonies  which  develop  so  enormously  the  pouch  into  which 
the  food  is  drawn,  that  the  abdomen  becomes  little  else  than  a 
great  bladder  out  of  which  the  head,  thorax,  and  legs  protrude. 
This,  it  is  thought,  cannot  be  accounted  for  otherwise  than  as  a 
consequence  of  specially  endowed  eggs,  which  it  has  become 
profitable  to  the  community  for  the  queen  to  produce.  But  the 
explanation  fits  in  quite  easily  with  the  view  I  have  set  forth. 
No  one  will  deny  that  the  taking  in  of  food  is  the  deepest  of 
vital  requirements,  and  the  correlative  instinct  a  dominant  one ; 
nor  will  any  one  deny  that  the  instinct  of  feeding  young  is  less 
deeply  seated — comes  later  in  order  of  time.  So,  too,  every  one 
will  admit  that  the  worker-bee  or  worker-ant  before  regurgitat- 
ing food  into  the  mouth  of  a  larva  must  first  of  all  take  it  in. 
Hence,  alike  in  order  of  time  and  necessity,  it  is  to  be  assumed 
that  development  of  the  nervous  structures  which  guide  self 
nutrition,  precedes  development  of  the  nervous  structures  which 
guide  the  feeding  of  larvae.  What,  then,  will  in  some  cases 
happen,  supposing  there  is  an  arrested  development  consequent 
on  innutrition  ?  It  will  in  some  cases  happen  that  while  the 
nervous  centres  prompting  and  regulating  deglutition  aro  fully 


684  APPENDIX  B. 

formed,  the  formation  of  those  prompting  and  regulating  the 
regurgitation  of  the  food  into  the  mouths  of  larvae  are  arrested. 
What  will  be  the  consequence  ?  The  life  of  the  worker  is  mainly 
passed  in  taking  in  food  and  putting  it  out  again.  If  the  putting 
out  is  stopped  its  life  will  be  mainly  passed  in  taking  in  food. 
The  receptacle  will  go  on  enlarging  and  it  will  eventually  assume 
the  monstrous  form  that  we  see.* 

Here,  however,  to  exclude  misinterpretations,  let  me  explain. 
I  by  no  means  deny  that  variation  and  selection  have  produced, 
in  these  insect-communities,  certain  effects  such  as  Mr.  Darwin 
suggested.  Doubtless  ant-queens  vary ;  doubtless  there  are  varia- 
tions in  their  eggs ;  doubtless  differences  of  structure  in  the  re- 
sulting progeny  sometimes  prove  advantageous  to  the  stirp,  and 
originate  slight  modifications  of  the  species.  But  such  changes, 
legitimately  to  be  assumed,  are  changes  in  single  parts — in  single 
organs  or  portions  of  organs.  Admission  of  this  does  not  in- 
volve admission  that  there  can  take  place  numerous  correlated 
variations  in  different  and  often  remote  parts,  which  must  take 
place  simultaneously  or  else  be  useless.  Assumption  of  this  is 
what  Professor  Weismann's  argument  requires,  and  assumption 
of  this  we  have  seen  to  be  absurd. 

Before  leaving  the  general  problem  presented  by  the  social 
insects,  let  me  remark  that  the  various  complexities  of  action 
not  explained  by  inheritance  from  pre-social  or  semi-social  types, 
are  probably  due  to  accumulated  and  transmitted  knowledge.  I 
recently  read  an  account  of  the  education  of  a  butterfly,  carried 
to  the  extent  that  it  became  quite  friendly  with  its  protector 
and  would  come  to  be  fed.  If  a  non-social  and  relatively  unin- 
telligent insect  is  capable  of  thus  far  consciously  adjusting  its 
actions,  then  it  seems  a  reasonable  supposition  that  in  a  com- 
munity of  social  insects  there  has  arisen  a  mass  of  experience  and 
usage  into  which  each  new  individual  is  initiated  ;  just  as  happens 
among  ourselves.  We  have  only  to  consider  the  chaos  which 
would  result  were  we  suddenly  bereft  of  language,  and  if  the 
young  were  left  to  grow  up  without  precept  and  example,  to  see 
that  very  probably  the  polity  of  an  insect  community  is  made 
possible  by  the  addition  of  intelligence  to  instinct,  and  the  trans- 
mission of  information  through  sign-language. 

There  remains  now  the  question  of  panmixia,  which  stands 
exactly  where  it  did  when  I  published  the  "Rejoinder  to  Pro- 
fessor Weismann." 

*  This  interpretation  harmonizes  with  a  fact  which  I  learn  from  Prof. 
Riley,  that  there  are  gradations  in  this  development,  and  that  in  some  species 
the  ordinary  neuters  swell  their  abdomens  so  greatly  with  food  that  they  can 
hardly  get  home. 


INADEQUACY  OP  NATURAL  SELECTION,   ETC.      685 

After  showing  that  the  interpretation  I  put  upon  his  view  was 
justified  by  certain  passages  quoted  ;  and  after  pointing  out  that 
one  of  his  adherents  had  set  forth  the  view  which  I  combated — 
if  not  as  his  view  yet  as  supplementary  to  it ;  I  went  on  to  criti- 
cize the  view  as  set  forth  afresh  by  Professor  Weismann  himself. 
I  showed  that  as  thus  set  forth  the  actuality  of  the  supposed 
cause  of  decrease  in  disused  organs,  implies  that  minus  variations 
habitually  exceed  plus  variations — in  degree  or  in  number,  or  in 
both.  Unless  it  can  be  proved  that  such  an  excess  ordinarily 
occurs,  the  hypothesis  of  panmixia  has  no  place  ;  and  I  asked, 
where  is  the  proof  that  it  occurs. 

No  reply. 

Not  content  with  this  abstract  form  of  the  question  I  put  it 
also  in  a  concrete  form,  and  granted  for  the  nonce  Professor 
Weismann's  assumption :  taking  the  case  of  the  rudimentary  hind 
limbs  of  the  whale.  I  said  that  though,  during  those  early 
stages  of  decrease  in  which  the  disused  limbs  were  external, 
natural  selection  probably  had  a  share  in  decreasing  them,  since 
they  were  then  impediments  to  locomotion,  yet  when  they  became 
internal,  and  especially  when  they  had  dwindled  to  nothing  but 
remnants  of  the  femurs,  it  is  impossible  to  suppose  that  natural 
selection  played  any  part :  no  whale  could  have  survived  and 
initiated  a  more  prosperous  stirp  in  virtue  of  the  economy 
achieved  by  such  a  decrease.  The  operation  of  natural  selection 
being  out  of  the  question,  I  inquired  whether  such  a  decrease, 
say  of  one-half  when  the  femurs  weighed  a  few  ounces,  occurring 
in  one  individual,  could  be  supposed  in  the  ordinary  course  of 
reproduction  to  affect  the  whole  of  the  whale  species  inhabiting 
the  Arctic  Seas  and  the  North  Atlantic  Ocean  ;  and  so  on  with 
successive  diminutions  until  the  rudiments  had  reached  their 
present  minuteness.  I  asked  whether  such  an  interpretation  could 
be  rationally  entertained. 

No  reply. 

Now  in  the  absence  of  replies  to  these  two  questions  it  seems 
to  me  that  the  verdict  must  go  against  Professor  Weismann  by 
default.  If  he  has  to  surrender  the  hypothesis  of  panmixia,  what 
results  ?  All  that  evidence  collected  by  Mr.  Darwin  and  others, 
regarded  by  them  as  proof  of  the  inheritance  of  acquired  charac- 
ters, which  was  cavalierly  set  aside  on  the  strength  of  this  alleged 
process  of  panmixia,,  is  reinstated.  And  this  reinstated  evidence, 
joined  with  much  evidence  since  furnished,  suffices  to  establish 
the  repudiated  interpretation. 

In  the  printed  report  of  his  Romanes  Lecture,  after  fifty  pages 
of  complicated  speculations  which  we  are  expected  to  accept  as 
proofs,  Professor  Weismann  ends  by  saying,  in  reference  to  the 
case  of  the  neuter  insects  : — 


686  APPENDIX  B. 

"  This  case  is  of  additional  interest,  as  it  may  serve  to  convince  those 
naturalists  who  are  still  inclined  to  maintain  that  acquired  characters  are 
inherited,  and  to  support  the  Lamarckian  principle  of  development,  that  their 
Tiew  cannot  be  the  right  one.  It  has  not  proved  tenable  in  a  single  instance  " 
(P-  54). 

Most  readers  of  the  foregoing  pages  will  think  that  since  Pro- 
fessor Weismann  has  left  one  after  another  of  my  chief  theses 
without  reply,  this  is  rather  a  strong  assertion  ;  and  they  will 
still  further  raise  their  eyebrows  on  remembering  that,  as  I  have 
shown,  where  he  has  given  answers  his  answers  are  invalid. 

And  now  we  come  to  the  additions  which  I  indicated  at  the 
outset  as  having  to  be  made — certain  evidences  which  have  come 
to  light  since  this  controversy  commenced. 

When,  by  a  remembered  observation  made  in  boyhood,  joined 
with  the  familiar  fact  that  worker-larvae  can  be  changed  into  the 
larvae  of  queens  by  feeding,  I  was  led  to  suggest  that  probably 
all  the  variations  of  form  in  the  social  insects  are  consequent  on 
differences  of  nurture,  I  was  unaware  that  observations  and 
experiments  were  being  made  which  have  justified  this  suggestion. 
Professor  Grassi  has  recently  published  accounts  of  the  food- 
habits  of  two  European  species  of  Termites,  shewing  that  the 
various  forms  are  due  to  feeding.  He  is  known  to  be  a  most 
careful  observer,  and  some  of  the  most  curious  of  his  facts  are 
confirmed  by  the  collection  of  white  ants  exhibited  by  Dr.  David 
Sharp,  F.R.S.,  at  the  soiree  of  the  Royal  Society  in  May  last. 
He  has  favoured  me  with  the  following  account  of  Grassi's  results, 
which  I  publish  with  his  assent : — 

"  There  is  great  variety  as  to  the  constituents  of  the  community  and 
economy  of  the  species  in  White  Ants.  One  of  the  simplest  conditions  known 
is  that  studied  by  Grassi  in  the  case  of  the  European  species  Calotermes  flavi- 
collis.  In  this  species  there  is  no  worker  caste ;  the  adult  forms  are  only  of 
two  kinds,  viz.,  soldiers,  and  the  males  and  females ;  the  sexes  are  externally 
almost  indistinguishable,  and  there  are  males  and  females  of  soldiers  as  well 
as  of  the  winged  forms,  though  the  sexual  organs  do  not  undergo  their  full 
development  in  any  soldier  whether  male  or  female. 

"  The  soldier  is  not  however  a  mere  instance  of  simple  arrested  develop- 
ment. It  is  true  that  there  is  in  it  arrested  development  of  the  sexual  organs, 
but  this  is  accompanied  by  change  of  form  of  other  parts — changes  so  extreme 
that  one  would  hardly  suppose  the  soldier  to  have  any  connection  with  either 
the  young  or  the  adult  of  the  winged  forms. 

"  Now  according  to  Grassi  the  whole  of  the  individuals  when  born  are 
undifferentiated  forms  (except  as  to  sex),  and  each  one  is  capable  of  going  on 
the  natural  course  of  development  and  thus  becoming  a  winged  insect,  or  can 
be  deviated  from  this  course  and  made  into  a  soldier ;  this  is  accomplished  by 
the  White  Ants  by  special  courses  of  feeding. 

"  The  evidence  given  by  Grassi  is  not  conclusive  as  to  the  young  being  all 
born  alike ;  and  it  may  be  that  there  are  some  individuals  born  that  could 
not  be  deviated  from  the  natural  course  and  made  into  soldiers.  But  there 
is  one  case  which  seems  to  show  positively  that  the  deviation  Grassi  believes 


INADEQUACY  OF  NATURAL  SELECTION,   ETC.      687 

to  occur  is  real,  and  not  due  to  the  selection  by  the  ants  of  an  individual 
that  though  appearing  to  our  eyes  undifferentiated  is  not  really  so.  This  is 
that  an  individual  can  be  made  into  a  soldier  after  it  has  visibly  undergone 
one  half  or  more  of  the  development  into  a  winged  form.  The  Termites 
can  in  fact  operate  on  an  individual  that  has  already  acquired  the  rudi- 
ments of  wings  and  whose  head  is  totally  destitute  of  any  appearance  of 
the  shape  of  the  armature  peculiar  to  the  soldier,  and  can  turn  it  into  a 
soldier  ;  the  rudiments  of  the  wings  being  in  such  a  case  nearly  entirely 
re-absorbed." 

Grassi  has  been  for  many  years  engaged  in  investigating  these 
phenomena,  and  there  is  no  reason  for  rejecting  his  statement. 
We  can  scarcely  avoid  accepting  it,  and  if  so,  Professor  Weis- 
mann's  hypothesis  is  conclusively  disposed  of.  Were  there 
different  sets  of  "  determinants  "  for  the  soldier-form  and  for  the 
winged  sexual  form,  those  "  determinants  "  which  had  gone  a 
long  way  towards  producing  the  winged  sexual  form,  would  in- 
evitably go  on  to  complete  that  form,  and  could  not  have  their 
proclivity  changed  by  feeding. 

[Yet  more  evidence  to  the  like  effect  has  since  become  known. 
At  the  meeting  of  the  Entomological  Society,  on  March  14,  1894 
(reported  in  Nature,  March  29)  : — 

"Dr.  D.  Sharp,  F.R.S.,  exhibited  a  collection  of  white  ants  (Termites), 
formed  by  Mr.  G.  D.  Haviland  in  Singapore,  which  comprised  about  twelve 
species,  of  most  of  which  the  various  forms  were  obtained.  He  said  that 
Prof.  Grassi  had  recently  made  observations  on  the  European  species,  and  had 
brought  to  light  some  important  particulars ;  and  also  that  in  the  discussion 
that  had  recently  been  carried  on  between  Mr.  Herbert  Spencer  and  Prof. 
Weismann,  the  former  had  stated  that  in  his  opinion  the  different  forms  of 
social  insects  were  produced  by  nutrition.  Prof.  Grassi's  observations  showed 
this  view  to  be  correct,  and  the  specimens  now  exhibited  confirmed  one  of  the 
most  important  points  in  his  observations.  Dr.  Sharp  also  stated  that  Mr. 
Haviland  found  in  one  nest  eleven  neoteinic  queens — that  is  to  say,  individu- 
als having  the  appearance  of  the  queen  in  some  respects,  while  in  others  they 
are  still  immature." 

Another  similarly  conclusive  verification  I  published  in  Nature 
for  December  6,  1894,  under  the  title  "The  Origin  of  Classes 
among  the  '  Parasol '  Ants."  The  letter  ran  as  follows  : — 

"  Mr.  J.  H.  Hart  is  Superintendent  of  the  Royal  Botanic  Gardens  in  Trini 
dad.  He  has  sent  me  a  copy  of  his  report  presented  to  the  Legislative  Coun- 
cil in  March,  1893,  and  has  drawn  my  attention  to  certain  facts  contained  in 
it  concerning  the  'Parasol'  ants — the  leaf-cutting  ants  which  feed  on  the 
fungi  developed  in  masses  of  the  cut  leaves  carried  to  their  nests.  Both  Mr. 
Bates  and  Mr.  Belt  described  these  ants,  but  described,  it  seems,  different, 
though  nearly  allied,  species,  the  habits  of  which  are  partially  unlike.  As 
they  are  garden-pests,  Mr.  Hart  was  led  to  examine  into  the  development  and 
social  arrangements  of  these  ants ;  establishing,  to  that  end,  artificial  nests, 
after  the  manner  adopted  by  Sir  John  Lubbock.  Several  of  the  facts  set 
down  have  an  important  bearing  on  a  question  now  under  discussion.  The 
following  extracts,  in  which  they  are  named,  I  abridge  by  omitting  passages 
not  relevant  to  the  issue : — 

" '  The  history  of  my  nests  is  a*  follows :  Nos.  1  and  2  were  both  taken 


688  APPENDIX  B. 

(August  0)  on  the  same  day,  while  destroying  nests  in  the  Gardens,  and  were 
portions  of  separate  nests  but  of  the  same  species.  No.  3  was  procured  on 
September  6,  and  is  evidently  a  different  although  an  allied  species  to  Nos.  1 
and  2. 

" '  Finding  neither  of  my  nests  had  a  queen,  I  procured  one  from  another 
nest  about  to  be  destroyed,  and  placed  it  with  No.  1  nest.  It  was  received  by 
the  workers,  and  at  once  attended  by  a  numerous  retinue  in  royal  style.  On 
August  30  I  removed  the  queen  from  No.  1  and  placed  it  with  No.  2,  when  it 
was  again  received  in  a  most  loyal  manner.  .  .  . 

" '  Ants  taken  from  Nos.  1  and  2  and  placed  with  No.  3  were  immediately 
destroyed  by  the  latter,  and  even  the  soldiers  of  No.  3,  as  well  as  workers  or 
nurses,  were  destroyed  when  placed  with  Nos.  1  and  2. 

" '  In  nest  No.  2,  from  which  I  removed  the  queen  on  August  30,  there  are 
now  in  the  pupa  stage  several  queens  and  several  males.  The  forms  of  ant 
in  nests  Nos.  1  and  2  are  as  follows :  (a)  queen,  (b)  male  (both  winged,  but  the 
queen  loses  its  wings  after  marital  flight),  (c)  large  workers,  (d)  small  workers, 
and  (e)  nurses.  In  nest  No.  3  I  have  not  yet  seen  the  queen  or  male,  but 
it  possesses— (a)  soldier,  (b)  larger  workers,  (c)  smaller  workers,  and  (d) 
nurses;  but  these  are  different  in  form  to  those  of  nests  No.  1  and  No.  2. 
Probably  we  might  add  a  third  form  of  worker,  as  there  are  several  sizes  in 
the  nest.  .  .  . 

" '  It  is  curious  that  in  No.  1  nest,  from  which  the  queen  was  removed  on 
August  30,  new  queens  and  males  are  now  being  developed,  while  in  No.  2 
nest,  where  the  queen  is  at  present,  nothing  but  workers  have  been  brought 
out,  and  if  a  queen  larva  or  pupa  is  placed  there  it  is  at  once  destroyed, 
while  worker  larvae  or  pupae  are  amicably  received.  In  No.  3  all  the  eggs, 
larvae,  and  pupae  collected  with  the  nest  have  been  hatched,  and  no  eggs  have 
since  made  their  appearance  to  date.  There  is  no  queen  with  this  nest.  .  .  . 
On  November  14  I  attempted  to  prove  by  experiment  how  small  a  number  of 
"  parasol "  ants  it  required  to  form  a  new  colony.  I  placed  two  dozen  of  ants 
(one  dozen  workers  and  one  dozen  nurses)  in  two  separate  nests,  No.  4  and 
No.  5.  With  No.  4  I  placed  a  few  larvae  with  a  few  rose  petals  for  them  to 
manipulate.  With  No.  5  I  gave  a  small  piece  of  nest  covered  with  mycelium. 
On  the  16th  these  nests  were  destroyed  by  small  foraging  ants,  known  as  the 
"sugar"  or  "meat"  ant,  and  I  had  to  remove  them  and  replace  with  a  new 
colony.  My  notes  on  these  are  not  sufficiently  lengthy  to  be  of  much  im- 
portance. But  I  noted  four  eggs  laid  on  the  16th,  or  two  days  after  being 
placed  in  their  new  quarters;  no  queen  being  present.  The  experiment  is 
being  continued.  I  may  mention  that  in  No.  4  nest,  in  which  no  fungus  was 
present,  the  larvae  of  all  sizes  appeared  to  change  into  the  pupae  stage  at  once 
for  want  of  food  [a  fact  corresponding  with  the  fact  I  have  named  as  observed 
by  myself  sixty  years  ago  in  the  case  of  wasp  larvae].  The  circumstance  tends 
to  show  that  the  development  of  the  insect  is  influenced  entirely  by  the  feed- 
ing it  gets  in  the  larva  stage. 

" '  In  nest  No.  2  before  the  introduction  of  a  queen  there  were  no  eggs  or 
larvae.  The  first  worker  was  hatched  on  October  27,  or  fifty-seven  days  after- 
wards, and  a  continual  succession  has  since  been  maintained,  but  as  yet 
(November  19)  no  males  or  queens  have  made  their  appearance.' 

"  In  a  letter  accompanying  the  report,  Mr.  Hart  says : — 

" '  Since  these  were  published,  my  notes  go  to  prove  that  ants  can  practi- 
cally manufacture  at  will,  male,  female,  soldier,  worker,  or  nurse.  Some  of 
the  workers  are  capable  of  laying  eggs,  and  from  these  can  be  produced  all 
the  various  forms  as  well  as  from  a  queen's  egg. 

"'There  does  not,  however,  appear  to  be  any  difference  in  the  character  of 
the  food  ;  a-s  I  cannot  find  that,  the  larger  larvae  are  fed  with  anything  differ- 
ent to  thai-  given  to  the  smaller.' 


INADEQUACY  OF  NATURAL  SELECTION,  ETC.      689 

"  These  results  were  obtained  before  the  recent  discussion  of  the  question 
commenced,  and  joined  with  'the  other  evidence  entirely  dispose  of  those 
arguments  which  Prof.  Weismann  bases  on  facts  furnished  by  the  social 
insects."] 

The  other  piece  of  additional  evidence  I  have  referred  to,  is 
furnished  by  two  papers  contributed  to  The  Journal  of  Anatomy 
and  Physiology  for  October  1893  and  April  1894,  by  R.  Havelock 
Charles,  M.  D.,  &c.  &c.,  Professor  of  Anatomy  in  the  Medical 
College,  Lahore.  These  papers  set  forth  the  differences  between 
the  leg-bones  of  Europeans  and  those  of  the  Punjaub  people — 
differences  caused  by  their  respective  habits  of  sitting  in  chairs 
and  squatting  on  the  ground.  He  enumerates  more  than  twenty 
such  differences,  chiefly  in  the  structures  of  the  knee-joint  and 
ankle-joint.  From  the  resume  of  his  second  paper  I  quote  the 
following  passages,  which  sufficiently  show  the  data  and  the  in- 
ferences : — 

"  7.  The  habits  as  to  sitting  postures  of  Europeans  differ  from  those  of 
their  prehistoric  ancestors,  the  Cave-dwellers,  &c.,  who  probably  squatted  on 
the  ground. 

"  8.  The  sitting  postures  of  Orientals  are  the  same  now  as  ever.  They 
have  retained  the  habits  of  their  ancestors.  The  Europeans  have  not 
done  so. 

"  9.  Want  of  use  would  induce  changes  in  form  and  size,  and  so,  gradually, 
small  differences  would  be  integrated  till  there  would  be  total  disappearance 
of  the  markings  on  the  European  skeleton,  as  no  advantage  would  accrue  to 
him  from  the  possession  of  facets  on  his  bones  fitting  them  for  postures  not 
practised  by  him. 

"  10.  The  facets  seen  on  the  bones  of  the  Panjabi  infant  or  foetus  have 
been  transmitted  to  it  by  the  accumulation  of  peculiarities  gained  by  habit  in 
the  evolution  of  its  racial  type — in  which  an  acquisition  having  become  a  per- 
manent possession,  '  profitable  to  the  individual  under  its  conditions  of  life,'  is 
transmitted  as  a  useful  inheritance. 

"11.  These  markings  are  due  to  the  influence  of  certain  positions,  which 
are  brought  about  by  the  use  of  groups  of  muscles,  ami  they  are  the  definite 
results  produced  by  actions  of  these  muscles. 

"  12.  The  effects  of  the  use  of  the  muscles  mentioned  in  No.  11  are  trans- 
mitted to  the  offspring,  for  the  markings  are  present  in  the  fcetus-in-utero,  in 
the  child  at  birth,  and  in  the  infant. 

"13.  The  markings  are  instances  of  the  transmission  of  acquired  charac- 
ters, which  heritage  in  the  individual,  function  subsequently  develops." 

No  other  conclusion  appears  to  me  possible.  Panmixia,  even 
were  it  not  invalidated  by  its  unwarranted  assumption  as  above 
shown,  would  be  out  of  court :  the  case  is  not  a  case  of  either 
increase  or  decrease  of  size  but  of  numerous  changes  of  form. 
Simultaneous  variation  of  co-operative  parts  cannot  be  alleged, 
since  these  co-operative  parts  have  not  changed  in  one  way  but 
in  various  ways  and  degrees.  And  even  were  it  permissible  to 
suppose  that  the  required  different  variations  had  taken  place 
simultaneously,  natural  selection  cannot  be  supposed  to  have 
operated.  The  assumption  would  imply  that  in  the  struggle  for 


690  APPENDIX  B. 

existence,  individuals  of  the  European  races  who  were  less  capable 
than  others  of  crouching  and  squatting,  gained  by  those  minute 
changes  of  structure  which  incapacitated  them,  such  advantages 
that  their  stirps  prevailed  over  other  stirps — an  absurd  suppo- 
sition. 

And  now  I  must  once  more  point  out  that  a  grave  responsi- 
bility rests  on  biologists  in  respect  of  the  general  question  ;  since 
wrong  answers  lead,  among  other  effects,  to  wrong  beliefs  about 
social  affairs  and  to  disastrous  social  actions.  In  me  this  convic- 
tion has  unceasingly  strengthened.  Though  The  Origin  of  Species 
proved  to  me  that  the  transmission  of  acquired  characters  cannot 
be  the  sole  factor  in  organic  evolution,  as  I  had  assumed  in  So- 
cial Statics  and  in  The  Principles  of  Biology,  published  in  pre- 
Darwinian  days,  yet  I  have  never  wavered  in  the  belief  that  it  is 
a  factor  and  an  all-important  factor.  And  I  have  felt  more  and 
more  that  since  all  the  higher  sciences  are  dependent  on  the 
science  of  life,  and  must  have  their  conclusions  vitiated  if  a  fun- 
damental datum  given  to  them  by  the  teachers  of  this  science  is 
erroneous,  it  behoves  these  teachers  not  to  let  an  erroneous  datum 
pass  current :  they  are  called  on  to  settle  this  vexed  question  one 
way  or  other.  The  times  give  proof.  The  work  of  Mr.  Benjamin 
Kidd  on  Social  Evolution,  which  has  been  so  much  lauded,  takes 
Weismannism  as  one  of  its  data  ;  and  if  Weismannism  be  untrue, 
the  conclusions  Mr.  Kidd  draws  must  be  in  large  measure  erro- 
neous and  may  prove  mischievous. 

POSTSCRIPT. — Since  the  foregoing  pages  have  been  put  in  type 
there  has  appeared  in  Natural  Science  for  September,  an  abstract 
of  certain  parts  of  a  pamphlet  by  Professor  Oscar  Hertwig,  set- 
ting forth  facts  directly  bearing  on  Professor  Weismann's  doctrine 
respecting  the  distinction  between  reproductive  cells  and  somatic 
cells.  In  The  Principles  of  Biology,  §  77, 1  contended  that  repro- 
ductive cells  differ  from  other  cells  composing  the  organism,  only 
in  being  unspecialized.  And  in  support  of  the  hypothesis  that 
tissue-cells  in  general  have  a  reproductive  potentiality,  I  instanced 
the  cases  of  the  Begonia phyllomaniaca  and  Malaxis paludosa.  In 
the  thirty  years  which  have  since  elapsed,  many  facts  of  like  sig- 
nificance have  been  brought  to  light,  and  various  of  these  are 
given  by  Professor  Hertwig.  Here  are  some  of  them  : — 

"  Galls  are  produced  under  the  stimulus  of  the  insect  almost  anywhere 
on  the  surface  of  a  plant.  Yet  in  most  cases  these  galls,  in  a  sense  grown 
at  random  on  the  surface  of  a  plant,  when  placed  in  damp  earth  will  give 
rise  to  a  young  plant.  In  the  hydroid  Tubularia  mesembryanthcmum,  when 
the  polyp  heads  are  cut  off,  new  heads  arise.  But  if  both  head  and  root  be 
cut  off,  and  the  upper  end  be  inserted  in  the  mud,  then  from  the  original 
upper  end  not  head-polyps  but  root  filaments  will  arise,  while  from  the 
original  lower  end  not  root  filaments  but  head-polyps  will  grow.  .  .  . 


INADEQUACY  OF  NATUBAL  SELECTION,   ETC.       G91 

Driesch,  by  separating  the  first  two  and  the  first  four  segmentation  spheres 
of  an  Echinu*  ovum,  obtained  two  or  four  normal  plutei,  respectively  one 
half  and  a  quarter  of  the  normal  size.  ...  So,  also,  in  the  case  of 
uS  Wil 


ilson  obtained  a  normal,  but  proportionately  diminished 
embryo  with  complete  nervous  system  from  a  separated  sphere  of  a  two- 
or  four-  or  eight  celled  stage.  .  .  .  Chabry  obtained  norrral  embryos 
in  cases  where  some  of  the  segmentation-spheres  had  been  artificially  de- 
stroyed." 

These  evidences,  furnished  by  independent  observers,  unite  in 
showing,  firstly,  that  all  the  multiplying  cells  of  the  developing 
embryo  are  alike  ;  and,  secondly,  that  the  soma-cells  of  the  adult 
severally  retain,  in  a  latent  form,  all  the  powers  of  the  original 
embryo-  cell.  If  these  facts  do  not  disprove  absolutely  Professor 
Weismann's  hypothesis,  we  may  wonderingly  ask  what  facts  would 
disprove  it  ? 

Since  Hertwig  holds  that  all  the  cells  forming  an  organism  of 
any  species  primarily  consist  of  the  same  components,  I  at  first 
thought  that  his  hypothesis  was  identical  with  my  own  hypothesis 
of  "  physiological  units,"  or,  as  I  would  now  call  them,  constitu- 
tional units.  It  seems  otherwise,  however;  for  he  thinks  that 
each  cell  contains  "  only  those  material  particles  which  are  bearers 
of  cell-  properties,"  and  that  organs  "are  the  functions  of  cell- 
complexes."  To  this  it  may  be  replied  that  the  ability  to  form 
the  appropriate  cell-complexes,  itself  depends  upon  the  constitu- 
tional units  contained  in  the  cells. 


APPENDIX    C. 


THE  INHERITANCE  OF  FUNCTIONALLY-WROUGHT  MODIFI- 
CATIONS: A  SUMMARY. 

THE  assertion  that  changes  of  structure  caused  by  changes  of 
function  are  transmitted  to  descendants  is  continually  met  by  the 
question — Where  is  the  evidence  ?  When  some  facts  are  assigned 
in  proof,  they  are  pooh-poohed  as  insufficient.  If  after  a  time  the 
question  is  raised  afresh  and  other  facts  are  named,  there  is  a  like 
supercilious  treatment  of  them.  Successively  rejected  in  this  way, 
the  evidences  do  not  accumulate  in  the  minds  of  opponents ;  and 
hence  produce  little  or  no  effect.  When  they  are  brought  together, 
however,  it  turns  out  that  they  are  numerous  and  weighty.  We 
will  group  them  into  negative  and  positive. 

Negative  evidence  is  furnished  by  those  cases  in  which  traits 
otherwise  inexplicable  are  explained  if  the  structural  effects  of 
use  and  disuse  are  transmitted.  In  the  foregoing  chapters  and 
appendices  three  have  been  given. 

(1)  Co-adaptation  of  co-operative  parts  comes  first.     This  has 
been  exemplified  by  the  case  of  enlarged  horns  in  a  stag,  by  the 
case  of  an  animal  led  into  the  habit  of  leaping,  and  in  the  case  of 
the  giraffe  (cited  in  "  The  Factors  of  Organic  Evolution  ") ;  and 
it  has  been  shown  that  the  implied  co-adaptations  of  parts  cannot 
possibly  have  been  effected  by  natural  selection. 

(2)  The  possession  of  unlike  powers  of  discrimination  by  dif- 
ferent parts  of  the  human  skin,  was  named  as  a  problem  to  be 
solved  on  the  hypothesis  of  natural  selection  or  the  hypothesis  of 
panmixia;  and  it  was  shown  that  neither  of  these  can  by  any 
twisting  yield   a  solution.     But  the  facts   harmonize  with  the 
hypothesis  that  the  effects  of  use  are  inherited. 

(3)  Then  come  the  cases  of  those  rudimentary  organs  which, 
like   the   hind   limbs   of    the   whale,   have    nearly   disappeared. 
Dwindling  by  natural  selection  is  here  out  of  the  question ;  and 
dwindling  by  panmixia,  even  were  its  assumptions  valid,  would 
be  incredible.     But  as  a  sequence  of  disuse  the  change  is  clearly 
explained. 

Failure  to  solve  any  one  of  these  three  problems  would,  I  think, 


INHERITANCE  OP  FUNCTIONALLY-WROUGHT  CHANGES.  693 

alone  prove  the  Neo-Darwinian  doctrines  untenable  ;  and  the  fact 
that  we  have  three  unsolved  problems  seems  to  me  fatal. 

From  this  negative  evidence,  turn  now  to  the  positive  evi- 
dence. This  falls  into  several  groups. 

There  are  first  the  facts  collected  by  Mr.  Darwin,  implying 
functionally- altered  structures  in  domestic  animals.  The  hypo- 
thesis of  panmixia  is,  as  we  have  seen,  out  of  court ;  and  there- 
fore Mr.  Darwin's  groups  of  evidences  are  reinstated.  There  is 
the  changed  ratio  of  wing-bones  and  leg-bones  in  the  duck ;  there 
are  the  drooping  ears  of  cats  in  China,  of  horses  in  Russia,  of 
sheep  in  Italy,  of  guinea-pigs  in  Germany,  of  goats  and  cattle  in 
India,  of  rabbits,  pigs,  and  dogs  in  all  long-civilized  countries. 
Though  artificial  selection  has  come  into  play  where  drooping 
has  become  a  curious  trait  (as  in  rabbits),  and  has  probably 
caused  the  greater  size  of  ears  which  has  in  some  cases  gone  along 
with  diminished  muscular  power  over  them  ;  yet  it  could  not 
have  been  the  initiator,  and  has  not  been  operative  on  animals 
bred  for  profit.  Again  there  are  the  changes  produced  by  climate ; 
as  instance,  among  plants,  the  several  varieties  of  maize  estab- 
lished in  Germany  and  transformed  in  the  course  of  a  few  gene- 
rations. 

Facts  of  another  class  are  yielded  by  the  blind  inhabitants  of 
caverns.  One  who  studies  the  memoir  by  Mr.  Packard  on  The 
Cave  Fauna  of  North  America,  &c.,  will  be  astonished  at  the 
variety  of  types  in  which  degeneration  or  loss  of  the  eyes  has 
become  a  concomitant  of  life  passed  in  darkness.  A  great 
increase  in  the  force  of  this  evidence  will  be  recognized  on  learn- 
ing that  absence  or  extreme  imperfection  of  visual  organs  is 
found  also  in  creatures  living  in  perpetual  night  at  the  bottoms  of 
deep  oceans.  Endeavours  to  account  for  these  facts  otherwise 
than  by  the  effects  of  disuse  we  have  seen  to  be  futile. 

Kindred  evidence  is  yielded  by  decrease  of  the  jaws  in  those 
races  which  have  had  diminished  use  of  them — mankind  and 
certain  domestic  animals.  Relative  smallness  in  the  jaws  of 
civilized  men,  manifest  enough  on  comparison,  has  been  proved 
by  direct  measurement.  In  pet  dogs — pugs,  household  spaniels 
— we  find  associated  the  same  cause  with  the  same  effect.  Though 
there  has  been  artificial  selection,  yet  this  did  not  operate  until 
the  diminution  had  become  manifest.  Moreover  there  has  been 
diminution  of  the  other  structures  concerned  in  biting  :  there  are 
smaller  muscles,  feeble  zygomata,  and  diminished  areas  for  inser- 
tion of  muscles — traits  which  cannot  have  resulted  from  selec- 
tion, since  they  are  invisible  in  the  living  animal. 

In  abnormal  vision  produced  by  abnormal  use  of  the  eyes  we 
have  evidence  of  another  kind.  That  the  Germans,  among 
43 


694  APPENDIX  C. 

whom  congenital  short  sight  is  notoriously  prevalent,  have  been 
made  shortsighted  by  inheritance  of  modifications  due  to  con- 
tinual reading  of  print  requiring  close  attention,  is  by  some 
disputed.  It  is  strange,  however,  that  if  there  exists  no  causal 
connexion  between  them,  neither  trait  occurs  without  the  other 
elsewhere.  But  for  the  belief  that  there  is  a  causal  connexion  we 
have  the  verifying  testimony  of  oculists.  From  Dr.  Lindsay 
Johnson  I  have  cited  cases  within  his  professional  experience  of 
functionally-produced  myopia  transmitted  to  children  ;  and  he 
asserts  that  other  oculists  have  had  like  experiences. 

Development  of  the  musical  faculty  in  the  successive  members 
of  families  from  which  the  great  composers  have  come,  as  well  as 
in  the  civilized  races  at  large,  is  not  to  be  explained  by  natural 
selection.  Even  when  it  is  great,  the  musical  faculty  has  not  a 
life-saving  efficiency  as  compared  with  the  average  of  faculties  ; 
for  the  most  highly  gifted  have  commonly  passed  less  prosperous 
lives  and  left  fewer  offspring  than  have  those  possessed  of  ordi- 
nary abilities.  Still  less  can  it  be  said  that  the  musical  faculty 
in  mankind  at  large  has  been  developed  by  survival  of  the  fittest. 
No  one  will  assert  that  men  in  general  have  been  enabled  to 
survive  and  propagate  in  proportion  as  their  musical  appreciation 
was  great. 

The  transmission  of  nervous  peculiarities  functionally  pro- 
duced is  alleged  by  the  highest  authorities — Dr.  Savage,  presi- 
dent of  the  Neurological  Society,  and  Dr.  Hughlings  Jackson. 
The  evidence  they  assign  confirms,  and  is  confirmed  by,  that 
which  the  development  of  the  musical  faculty  above  named 
supplies. 

Here,  then,  we  have  sundry  groups  of  facts  directly  support- 
ing the  belief  that  functionally -wrought  modifications  descend 
from  parents  to  offspring. 

Now  let  us  consider  the  position  of  those  Darwinians  who  dis- 
sent from  Darwin,  and  who  make  light  of  all  this  evidence.  We 
might  naturally  suppose  that  their  own  hypothesis  is  unassailable. 
Yet,  strange  to  say,  they  admit  that  there  is  no  direct  proof  that 
any  species  has  been  established  by  natural  selection.  The  proof 
is  inferential  only. 

The  certainty  of  an  axiom  does  not  give  certainty  to  the 
deductions  drawn  from  it.  That  natural  selection  is,  and  always 
has  been,  operative  is  incontestable.  Obviously  I  should  be  the 
last  person  to  deny  that  survival  of  the  fittest  is  a  necessity  : 
its  negation  is  inconceivable.  The  Neo-Darwinians,  however, 
judging  from  their  attitude,  apparently  assume  that  firmness  of 
the  basis  implies  firmness  of  the  superstructure.  But  however 
high  may  be  the  probability  of  some  of  the  conclusions  drawn, 


INHERITANCE  OP  FUNCTIONALLY-WROUGHT  CHANGES.  (505 

none  of  them  can  have  more  than  probability  ;  while  some  of 
them  remain,  and  are  likely  to  remain,  very  questionable.  Ob- 
serve the  difficulties. 

(1)  The  general  argument  proceeds  upon  the  analogy  between 
natural  selection  and  artificial  selection.     Yet  all  know  that  the 
first  cannot  do  what  the  last  does.     Natural  selection  can  do 
nothing  more  than  preserve  those  of  which  the  aggregate  charac- 
ters  are   most   favourable   to   life.     It   cannot   pick   out    those 
possessed  of  one  particular  favourable  character,  unless  this  is  of 
extreme  importance. 

(2)  In  many  cases  a  structure  is  of  no  service  until  it  has 
reached  a  certain  development ;  and  it  remains  to  account  for 
that  increase  of  it  by  natural  selection  which  must  be  supposed 
to  take  place  before  it  reaches  the  stage  of  usefulness. 

(3)  Advantageous  variations,  not  preserved  in  nature  as  they 
are  by  the  breeder,  are  liable  to  be  swamped  by  crossing  or  to 
disappear  by  atavism. 

Now  whatever  replies  are  made,  their  component  propositions 
cannot  be  necessary  truths.  So  that  the  conclusion  in  each  case, 
however  reasonable,  cannot  claim  certainty  :  the  fabric  can  have 
no  stability  like  that  of  its  foundation. 

When  to  uncertainties  in  the  arguments  supporting  the  hypo- 
thesis we  add  its  inability  to  explain  facts  of  cardinal  significance, 
as  proved  above,  there  is  I  think  ground  for  asserting  that 
natural  selection  is  less  clearly  shown  to  be  a  factor  in  the  origin- 
ation of  species  than  is  the  inheritance  of  functionally- wrought 
changes. 

If,  finally,  it  is  said  that  the  mode  in  which  functionally- 
wrought  changes,  especially  in  small  parts,  so  affect  the  reproduc- 
tive elements  as  to  repeat  themselves  in  offspring,  cannot  be 
imagined — if  it  be  held  inconceivable  that  those  minute  changes 
in  the  organs  of  vision  which  cause  myopia  can  be  transmitted 
through  the  appropriately-modified  sperm-cells  or  germ-cells ; 
then  the  reply  is  that  the  opposed  hypothesis  presents  a  corre- 
sponding inconceivability.  Grant  that  the  habit  of  a  pointer  was 
produced  by  selection  of  those  in  which  an  appropriate  variation 
in  the  nervous  system  had  occurred  ;  it  is  impossible  to  imagine 
how  a  slightly-different  arrangement  of  a  few  nerve-cells  and 
fibres  could  be  conveyed  by  a  spermatozoon.  So  too  it  is  im- 
possible to  imagine  how  in  a  spermatozoon  there  can  be  conveyed 
the  480,000  independent  variables  required  for  the  construction 
of  a  single  peacock's  feather,  each  having  a  proclivity  towards  its 
proper  place.  Clearly  the  ultimate  process  by  which  inheritance 
is  effected  in  either  case  passes  comprehension  ;  and  in  this  respect 
neither  hypothesis  has  an  advantage  over  the  other. 


APPENDIX    D. 


ON  ALLEGED   "SPONTANEOUS   GENERATION,"  AND   ON  THE 
HYPOTHESIS   OF  PHYSIOLOGICAL   UNITS. 

[The  following  letter,  originally  written  for  publication  in  the 
North  American  Review,  but  declined  by  the  Editor  in  pursuance 
of  a  general  rule,  and  eventually  otherwise  published  in  the  United 
States,  I  have  thought  well  to  append  to  this  first  volume  of  the  Prin- 
ciples of  Biology.  /  do  this  because  the  questions  which  it  discusses 
are  dealt  with  in  this  volume  ;  and  because  the  further  explanations 
it  furnishes  seem  needful  to  prevent  misapprehensions.] 

The  Editor  of  the  North  American  Review. 

SIR, 

It  is  in  most  cases  unwise  to  notice  adverse  criticisms. 
Either  they  do  not  admit  of  answers  or  the  answers  may  be  left  to 
the  penetration  of  readers.  When,  however,  a  critic's  allegations 
touch  the  fundamental  propositions  of  a  book,  and  especially  when 
they  appear  in  a  periodical  having  the  position  of  the  North  Ameri- 
can Review,  the  case  is  altered.  For  these  reasons  the  article  on 
"  Philosophical  Biology,"  published  in  your  last  number,  demands 
from  me  an  attention  which  ordinary  criticisms  do  not. 

It  is  the  more  needful  for  me  to  notice  it,  because  its  two  leading 
objections  have  the  one  an  actual  fairness  and  the  other  an  apparent 
fairness ;  and  in  the  absence  of  explanations  from  me,  they  will  be 
considered  as  substantiated  even  by  many,  or  perhaps  most,  of  those 
who  have  read  the  work  itself — much  more  by  those  who  have  not 
read  it.  That  to  prevent  the  spread  of  misapprehensions  I  ought  to 
say  something,  is  further  shown  by  the  fact  that  the  same  two  ob- 
jections have  already  been  made  in  England — the  one  by  Dr. 
Child,  of  Oxford,  in  his  Essays  on  Physiological  Subjects,  and  the 
other  by  a  writer  in  the  Westminster  Review  for  July,  1 865. 

In  the  note  to  which  your  reviewer  refers,  I  have,  as  he  says, 
tacitly  repudiated  the  belief  in  "  spontaneous  generation ; "  and 
that  I  have  done  this  in  such  a  way  as  to  leave  open  the  door  for 
the  interpretation  given  by  him  is  true.  Indeed  the  fact  that  Dr. 
Child,  whose  criticism  is  a  sympathetic  one,  puts  the  same  con- 
struction on  this  note,  proves  that  your  reviewer  has  but  drawn 
what  seems  to  be  a  necessary  inference.  Nevertheless,  the  infer- 
ence is  one  which  I  did  not  intend  to  be  drawn. 

In  explanation,  let  me  at  the  outset  remark  that  I  am  placed  at  a 
disadvantage  in  having  had  to  omit  that  part  of  the  System  of  Phi- 
losophy which  deals  with  Inorganic  Evolution.  In  the  original  pro- 
gramme will  be  found  a  parenthetic  reference  to  this  omitted  part, 
which  should,  as  there  stated,  precede  the  Principles  of  Biology. 


ALLEGED  SPONTANEOUS  GENERATION,   ETC.       697 

Two  volumes  are  missing.  The  closing  chapter  of  the  second,  were 
it  written,  would  deal  with  the  evolution  of  organic  matter — the 
step  preceding  the  evolution  of  living  forms.  Habitually  carrying 
with  me  in  thought  the  contents  of  this  unwritten  chapter,  I  have, 
in  some  cases,  expressed  myself  as  though  the  reader  had  it  before 
him ;  and  have  thus  rendered  some  of  my  statements  liable  to  mis- 
constructions. Apart  from  this,  however,  the  explanation  of  the  ap- 
parent inconsistency  is  very  simple,  if  not  very  obvious.  In  the  first 
place,  I  do  not  believe  in  the  "  spontaneous  generation  "  commonly 
alleged,  and  referred  to  in  the  note  ;  and  so  little  have  I  associated 
in  thought  this  alleged  "  spontaneous  generation  "  which  I  disbe- 
lieve, with  the  generation  by  evolution  which  I  do  believe,  that  the 
repudiation  of  the  one  never  occurred  to  me  as  liable  to  be  taken  for 
repudiation  of  the  other.  That  creatures  having  quite  specific  struc- 
tures are  evolved  in  the  course  of  a  few  hours,  without  antecedents 
calculated  to  determine  their  specific  forms,  is  to  me  incredible. 
Not  only  the  established  truths  of  Biology,  but  the  established 
truths  of  science  in  general,  negative  the  supposition  that  organisms 
having  structures  definite  enough  to  identify  them  as  belonging  to 
known  genera  and  species,  can  be  produced  in  the  absence  of  germs 
derived  from  antecedent  organisms  of  the  same  genera  and  species. 
If  there  can  suddenly  be  imposed  on  simple  protoplasm  the  organi- 
zation which  constitutes  it  a  Paramoecium,  I  see  no  reason  why 
animals  of  greater  complexity,  or  indeed  of  any  complexity,  may 
not  be  constituted  after  the  same  manner.  In  brief,  I  do  not  accept 
these  alleged  facts  as  exemplifying  Evolution,  because  they  imply 
something  immensely  beyond  that  which  Evolution,  as  I  understand 
it,  can  achieve.  In  the  second  place,  my  disbelief  extends  not  only 
to  the  alleged  cases  of  "  spontaneous  generation,"  but  to  every  case 
akin  to  them.  The  very  conception  of  spontaneity  is  wholly  incon- 
gruous with  the  conception  of  Evolution.  For  this  reason  I  regard 
as  objectionable  Mr.  Darwin's  phrase  "spontaneous  variation" 
(as  indeed  he  does  himself) ;  and  I  have  sought  to  show  that  there 
are  always  assignable  causes  of  variation.  No  form  of  Evolution, 
inorganic  or  organic,  can  be  spontaneous ;  but  in  every  instance 
the  antecedent  forces  must  be  adequate  in  their  quantities,  kinds, 
and  distributions,  to  work  the  observed  effects.  Neither  the  al- 
leged cases  of  "  spontaneous  generation,"  nor  any  imaginable  cases 
in  the  least  allied  to  them,  fulfil  this  requirement. 

If,  accepting  these  alleged  cases  of  "  spontaneous  generation," 
I  had  assumed,  as  your  reviewer  seems  to  do,  that  the  evolution  of 
organic  life  commenced  in  an  analogous  way  ;  then,  indeed,  I  should 
have  left  myself  open  to  a  fatal  criticism.  This  supposed  "  spon- 
taneous generation "  habitually  occurs  in  menstrua  that  contain 
either  organic  matter,  or  matter  originally  derived  from  organisms  ; 
and  such  organic  matter,  proceeding  in  all  known  cases  from  or- 
ganisms of  a  higher  kind,  implies  the  pre-existence  of  such  higher 


698  APPENDIX  D. 

organisms.  By  what  kind  of  logic,  then,  is  it  inferrible  that  organic 
life  was  initiated  after  a  manner  like  that  in  which  Infusoria  are 
said  to  be  now  spontaneously  generated  ?  Where,  before  life  com- 
menced, were  the  superior  organisms  from  which  these  lowest  or- 
ganisms obtained  their  organic  matter  ?  Without  doubting  that 
there  are  those  who,  as  the  reviewer  says,  "  can  penetrate  deeper 
than  Mr.  Spencer  has  done  into  the  idea  of  universal  evolution," 
and  who,  as  he  contends,  prove  this  by  accepting  the  doctrine  of 
"  spontaneous  generation  "  ;  I  nevertheless  think  that  I  can  pene- 
trate deep  enough  to  see  that  a  tenable  hypothesis  respecting  the 
origin  of  organic  life  must  be  reached  by  some  other  clue  than  that 
furnished  by  experiments  on  decoction  of  hay  and  extract  of  beef. 

From  what  I  do  not  believe,  let  me  now  pass  to  what  I  do  be- 
lieve. Granting  that  the  formation  of  organic  matter,  and  the  evo- 
lution of  life  in  its  lowest  forms,  may  go  on  under  existing  cos- 
mical  conditions ;  but  believing  it  more  likely  that  the  formation 
of  such  matter  and  such  forms,  took  place  at  a  time  when  the  heat 
of  the  Earth's  surface  was  falling  through  those  ranges  of  tempera- 
ture at  which  the  higher  organic  compounds  are  unstable ;  1  con- 
ceive that  the  moulding  of  such  organic  matter  into  the  simplest 
types,  must  have  commenced  with  portions  of  protoplasm  more 
minute,  more  indefinite,  and  more  inconstant  in  their  characters, 
than  the  lowest  Rhizopods — less  distinguishable  from  a  mere  frag- 
ment of  albumen  than  even  the  Protogenes  of  Professor  Haeckel. 
The  evolution  of  specific  shapes  must,  like  all  other  organic  evolu- 
tion, have  resulted  from  the  actions  and  reactions  between  such  in- 
cipient types  and  their  environments,  and  the  continued  survival 
of  those  which  happened  to  have  specialities  best  fitted  to  the 
specialities  of  their  environments.  To  reach  by  this  process  the 
comparatively  well-specialized  forms  of  ordinary  Infusoria,  must, 
I  conceive,  have  taken  an  enormous  period  of  time. 

To  prevent,  as  far  as  may  be,  future  misapprehension,  let  me 
elaborate  this  conception  so  as  to  meet  the  particular  objections 
raised.  The  reviewer  takes  for  granted  that  a  "  first  organism  " 
must  be  assumed  by  me,  as  it  is  by  himself.  But  the  conception  of  a 
"  first  organism,"  in  anything  like  the  current  sense  of  the  words,  is 
wholly  at  variance  with  conception  of  evolution  ;  and  scarcely  less 
at  variance  with  the  facts  revealed  by  the  microscope.  The  lowest 
living  things  are  not  properly  speaking  organisms  at  all ;  for  they 
have  no  distinctions  of  parts — no  traces  of  organization.  It  is  al- 
most a  misuse  of  language  to  call  them  "  forms"  of  life  :  not  only  are 
their  outlines,  when  distinguishable,  too  unspecific  for  description, 
but  they  change  from  moment  to  moment  and  are  never  twice  alike, 
either  in  two  individuals  or  in  the  same  individual.  Even  the  word 
"  type  "  is  applicable  in  but  a  loose  way  ;  for  there  is  little  constancy 
in  their  generic  characters :  according  as  the  surrounding  conditions 
determine,  they  undergo  transformations  now  of  one  kind  and  now  of 


ALLEGED  SPONTANEOUS  GENERATION,   ETC.        099 

another.  And  the  vagueness,  the  inconstancy,  the  want  of  appre- 
ciable structure,  displayed  by  the  simplest  of  living  things  as  we 
now  see  them,  are  characters  (or  absences  of  characters)  which,  on 
the  hypothesis  of  Evolution,  must  have  been  still  more  decided 
when,  as  at  first,  no  "  forms,"  no  "types,"  no  "  specific  shapes,"  had 
been  moulded.  That  "  absolute  commencement  of  organic  life  on 
the  globe,"  which  the  reviewer  says  I  "  cannot  evade  the  admission 
of,"  I  distinctly  deny.  The  affirmation  of  universal  evolution  is  in 
itself  the  negation  of  an  "  absolute  commencement "  of  anything. 
Construed  in  terms  of  evolution,  every  kind  of  being  is  conceived  as 
a  product  of  modifications  wrought  by  insensible  gradations  on  a 
pre-existing  kind  of  being ;  and  this  holds  as  fully  of  the  supposed 
"  commencement  of  organic  life  "  as  of  all  subsequent  developments 
of  organic  life.  It  is  no  more  needful  to  suppose  an  "  absolute 
commencement  of  organic  life  "  or  a  "  first  organism,"  than  it  is 
needful  to  suppose  an  absolute  commencement  of  social  life  and  a 
first  social  organism.  The  assumption  of  such  a  necessity  in  this 
last  case,  made  by  early  speculators  with  their  theories  of  "social 
contracts "  and  the  like,  is  disproved  by  the  facts ;  and  the  facts, 
so  far  as  they  are  ascertained,  disprove  the  assumption  of  such  a 
necessity  in  the  first  case.  That  organic  matter  was  not  produced 
all  at  once,  but  was  reached  through  steps,  we  are  well  warranted 
in  believing  by  the  experiences  of  chemists.  Organic  matters  are 
produced  in  the  laboratory  by  what  we  may  literally  call  artificial 
evolution.  Chemists  find  themselves  unable  to  form  these  complex 
combinations  directly  from  their  elements ;  but  they  succeed  in  form- 
ing them  indirectly,  by  successive  modifications  of  simpler  combina- 
tions. In  some  binary  compound,  one  element  of  which  is  present 
in  several  equivalents,  a  change  is  made  by  substituting  for  one  of 
these  equivalents  an  equivalent  of  some  other  element ;  so  producing 
a  ternary  compound.  Then  another  of  the  equivalents  is  replaced, 
and  so  on.  For  instance,  beginning  with  ammonia,  N  II3,  a  higher 
form  is  obtained  by  .replacing  one  of  the  atoms  of  hydrogen  by 
an  atom  of  methyl,  so  producing  methyl-amine,  N  (C  H3  H2) ; 
and  then,  under  the  further  action  of  methyl,  ending  in  a  further 
substitution,  there  is  reached  the  still  more  compound  substance 
dimethyl-amine,  N  (C  H3)  (C  H3)  H.  And  in  this  manner  highly 
complex  substances  are  eventually  built  up.  Another  character- 
istic of  their  method  is  no  less  significant.  Two  complex  com- 
pounds are  employed  to  generate,  by  their  action  upon  one  an- 
other, a  compound  of  still  greater  complexity :  different  hetero- 
geneous molecules  of  one  stage,  become  parents  of  a  molecule  a 
stage  higher  in  heterogeneity.  Thus,  having  built  up  acetic  acid 
out  of  its  elements,  and  having  by  the  process  of  substitution  de- 
scribed above,  changed  the  acetic  acid  into  propionic  acid,  and  pro- 

pionic  into  butyric,  of  which  the  formula  is  j  ^  ^  m3Q\  r  '•> 


700  APPENDIX  D. 

this  complex  compound,  by  operating  on  another  complex 
compound,  such  as  the  dimethyl- amine  named  above,  gene- 
rates one  of  still  greater  complexity,  butyrate  of  dimethyl-amine 

|  C  (0<JLO)  HS)  H  1  N  <C  HS)  (°  HS)  H'  See'  then'  the  re' 
markable  parallelism.  The  progress  towards  higher  types  of  or- 
ganic molecules  is  effected  by  modifications  upon  modifications ; 
as  throughout  Evolution  in  general.  Each  of  these  modifications  is 
a  change  of  the  molecule  into  equilibrium  with  its  environment — an 
adaptation,  as  it  were,  to  new  surrounding  conditions  to  which  it  is 
subjected  ;  as  throughout  Evolution  in  general.  Larger,  or  more 
integrated,  aggregates  (for  compound  molecules  are  such)  are  suc- 
cessively generated ;  as  throughout  Evolution  in  general.  More 
complex  or  heterogeneous  aggregates  are  so  made  to  arise,  one  out 
of  another ;  as  throughout  Evolution  in  general.  A  geometrically- 
increasing  multitude  of  these  larger  and  more  complex  aggregates 
so  produced,  at  the  same  time  results  ;  as  throughout  Evolution  in 
general.  And  it  is  by  the  action  of  the  successively  higher  forms 
on  one  another,  joined  with  the  action  of  environing  conditions,  that 
the  highest  forms  are  reached ;  as  throughout  Evolution  in  general. 
When  we  thus  see  the  identity  of  method  at  the  two  extremes 
— when  we  see  that  the  general  laws  of  evolution,  as  they  are  exem- 
plified in  known  organisms,  have  been  unconsciously  conformed  to 
by  chemists  in  the  artificial  evolution  of  organic  matter ;  we  can 
scarcely  doubt  that  these  laws  were  conformed  to  in  the  natural 
evolution  of  organic  matter,  and  afterwards  in  the  evolution  of  the 
simplest  organic  forms.  In  the  early  world,  as  in  the  modern 
laboratory,  inferior  types  of  organic  substances,  by  their  mutual 
actions  under  fit  conditions,  evolved  the  superior  types  of  organic 
substances,  ending  in  organizable  protoplasm.  And  it  can  hardly 
be  doubted  that  the  shaping  of  organizable  protoplasm,  which  is  a 
substance  modifiable  in  multitudinous  ways  with  extreme  facility, 
went  on  after  the  same  manner.  As  I  learn  from  one  of  our 
first  chemists,  Prof.  Frankland,  protein  is  capable  of  existing 
under  probably  at  least  a  thousand  isomeric  forms ;  and,  as 
we  shall  presently  see,  it  is  capable  of  forming,  with  itself 
and  other  elements,  substances  yet  more  intricate  in  composi- 
tion, that  are  practically  infinite  in  their  varieties  of  kind. 
Exposed  to  those  innumerable  modifications  of  conditions  which 
the  Earth's  surface  afforded,  here  in  amount  of  light,  there  in 
amount  of  heat,  and  elsewhere  in  the  mineral  quality  of  its  aqueous 
medium,  this  extremely  changeable  substance  must  have  undergone 
now  one,  now  another,  of  its  countless  metamorphoses.  And  to  the 
mutual  influences  of  its  metamorphic  forms  under  favouring  con- 
ditions, we  may  ascribe  the  production  of  the  still  more  composite, 
still  more  sensitive,  still  more  variously-changeable  portions  of 
organic  matter,  which,  in  masses  more  minute  and  simpler  than 


ALLEGED  SPONTANEOUS  GENERATION,  ETC.   701 

existing  Protozoa,  displayed  actions  verging  little  by  little 
into  those  called  vital — actions  which  protein  itself  exhibits  in  a 
certain  degree,  and  which  the  lowest  known  living  things  exhibit 
only  in  a  greater  degree.  Thus,  setting  out  with  inductions  from 
the  experiences  of  organic  chemists  at  the  one  extreme,  and 
with  inductions  from  the  observations  of  biologists  at  the  other 
extreme,  we  are  enabled  deductively  to  bridge  the  interval — 
are  enabled  to  conceive  how  organic  compounds  were  evolved,  and 
how,  by  a  continuance  of  the  process,  the  nascent  life  displayed  in 
these  became  gradually  more  pronounced.  And  this  it  is  which 
has  to  be  explained,  and  which  the  alleged  cases  of  "  spontaneous 
generation  "  would  not,  were  they  substantiated,  help  us  in  the 
least  to  explain. 

It  is  thus  manifest,  I  think,  that  I  have  not  fallen  into  the  alleged 
inconsistency.  Nevertheless,  I  admit  that  your  reviewer  w<ts 
justified  in  inferring  this  inconsistency ;  and  I  take  blame  to  my- 
self for  not  having  seen  that  the  statement,  as  1  have  left  it,  is 
open  to  misconstruction. 

I  pass  now  to  the  second  allegation — that  in  ascribing  to  certain 
specific  molecules,  which  I  have  called  "  physiological  units,"  the 
aptitude  to  build  themselves  into  the  structure  of  the  organism  to 
which  they  are  peculiar,  I  have  abandoned  my  own  principle,  and 
have  assumed  something  beyond  the  re-distribution  of  Matter  and 
Motion.  As  put  by  the  reviewer,  his  case  appears  to  be  well  made 
out ;  and  that  he  is  not  altogether  unwarranted  in  so  putting  it, 
may  be  admitted.  Nevertheless,  there  does  not  in  reality  exist  the 
supposed  incongruity. 

Before  attempting  to  make  clear  the  adequacy  of  the  conception 
which  I  am  said  to  have  tacitlv  abandoned  as  insufficient,  let  me 
remove  that  excess  of  improbability  the  reviewer  gives  to  it,  by  the 
extremely-restricted  meaning  with  which  he  uses  the  word  mechani- 
cal. In  discussing  a  proposition  of  mine  he  says  : — 

"He  then  cites  certain  remarks  of  Mr.  Paget  on  the  permanent  effects 
wrought  in  the  blood  by  the  poison  of  scarlatina  and  small-pox,  as  justifying 
the  belief  that  such  a  '  power '  exists,  and  attributes  the  repair  of  a  wasted 
tissue  to  '  forces  analogous  to  those  by  which  a  crystal  reproduces  its  lost 
apex.'  (Neither  of  which  phenomena,  however,  is  explicable  by  mechanical 
causes.) " 

Were  it  not  for  the  deliberation  with  which  this  last  statement  is 
made,  I  should  take  it  for  a  slip  of  the  pen.  As  it  is,  however,  I 
have  no  course  left  but  to  suppose  the  reviewer  unaware  of  the  fact 
that  molecular  actions  of  all  kinds  are  now  not  only  conceived  as 
mechanical  actions,  but  that  calcul  itions  based  on  this  conception  of 
them,  bring  out  the  results  that  correspond  with  observation.  There 
is  no  kind  of  re-arrangement  among  molecules  (crystallization 
being  one)  which  the  modern  physicist  does  not  think  of, 


702  APPENDIX  D. 

and  correctly  reason  upon,  in  terms  of  forces  and  motions  like 
those  of  sensible  masses.  Polarity  is  regarded  as  a  resultant  of 
such  forces  and  motions ;  and  when,  as  happens  in  many  cares, 
light  changes  the  molecular  structure  of  a  crystal,  and  alters  its 
polarity,  it  does  this  by  impressing,  in  conformity  with  mechanical 
laws,  new  motions  on  the  constituent  molecules.  That  the  reviewer 
should  present  the  mechanical  conception  under  so  extremely  limited 
a  form,  is  the  more  surprising  to  me  because,  at  the  outset  of  the 
very  work  he  reviews,  I  have,  in  various  passages,  based  inferences 
on  those  immense  extensions  of  it  which  he  ignores ;  indicating, 
for  example,  the  interpretation  it  yields  of  the  inorganic  chemical 
changes  effected  by  heat,  and  the  organic  chemical  changes  effected 
by  light  (Principles  of  Biology,  §  13). 

Premising,  then,  that  the  ordinary  idea  of  mechanical  action 
must  be  greatly  expanded,  let  us  enter  upon  the  question  at  issue — 
the  sufficiency  of  the  hypothesis  that  the  structure  of  each  organ- 
ism is  determined  by  the  polarities  of  the  special  molecules,  or 
physiological  units,  peculiar  to  it  as  a  species,  which  necessitate 
tendencies  towards  special  arrangements.  My  proposition  and 
the  reviewer's  criticism  upon  it,  will  be  most  conveniently  pre- 
sented if  I  quote  in  full  a  passage  of  his  from  which  I  have  already 
extracted  some  expressions.  He  says  : — 

"  It  will  be  noticed,  however,  that  Mr.  Spencer  attributes  the  possession 
of  these  '  tendencies,'  or  '  proclivities,'  to  natural  inheritance  from 
ancestral  organisms ;  and  it  may  be  argued  that  he  thus  saves  the 
mechanist  theory  and  his  own  consistency  at  the  same  time,  inasmuch  as 
he  derives  even  the  'tendencies'  themselves  ultimately  from  the  environ- 
ment. To  this  we  reply,  that  Mr.  Spencer,  who  advocates  the  nebular 
hypothesis,  cannot  evade  the  admission  of  an  absolute  commencement  of 
organic  life  on  the  globe,  and  that  the  'formative  tendencies,'  without 
which  he  cannot  explain  the  evolution  of  a  single  individual,  could  not 
have  been  inherited  by  the  first  organism.  Besides,  by  his  virtual  denial 
of  spontaneous  generation,  he  denies  that  the  first  organism  was  evolved 
out  of  the  inorganic  world,  and  thus  shuts  himself  off  from  the  argument 
(otherwise  plausible)  that  its  '  tendencies '  were  ultimately  derived  from  the 
environment." 

This  assertion  is  already  in  great  measure  disposed  of  by  what 
has  been  said  above.  Holding  that,  though  not  "  spontaneously 
generated,"  those  minute  portions  of  protoplasm  which  first  dis- 
played in  the  feeblest  degree  that  changeability  taken  to  imply  life, 
were  evolved,  I  am  not  debarred  from  the  argument  that  the  "ten- 
dencies "  of  the  physiological  units  are  derived  from  the  inherited 
effects  of  environing  actions.  If  the  conception  of  a  "  first  organ- 
ism "  were  a  necessary  one,  the  reviewer's  objection  would  be  valid. 
If  there  were  an  "absolute  commencement"  of  life,  a  definite  line 
parting  organic  matter  from  the  simplest  living  forms,  I  should  be 
placed  in  the  predicament  he  describes.  But  as  the  doctrine  of 
Evolution  itself  tacitly  negatives  any  such  distinct  separation ;  and 
as  the  negation  is  the  more  confirmed  by  the  facts  the  more  we 


ALLEGED  SPONTANEOUS  GENERATION,   ETC.       703 

know  of  them  ;  I  do  not  feel  that  I  am  entangled  in  the  alleged 
difficulty.  My  reply  might  end  here  ;  but  as  the  hypothesis  in 
question  is  one  not  easily  conceived,  and  very  apt  to  be  misun- 
derstood, I  will  attempt  a  further  elucidation  of  it. 

Much  evidence  now  conspires  to  show  that  molecules  of  the  sub- 
stances we  call  elementary  are  in  reality  compound ;  and  that,  by 
the  combination  of  these  with  one  another,  and  re-combinations  of 
the  products,  there  are  formed  systems  of  systems  of  molecules,  un- 
imaginable in  their  complexity.  Step  by  step  as  the  aggregate 
molecules  so  resulting,,  grow  larger  and  increase  in  heterogeneity, 
they  become  more  unstable,  more  readily  transformable  by  small 
forces,  more  capable  of  assuming  various  characters.  Those  com- 
posing organic  matter  transcend  all  others  in  size  and  intricacy  of 
structure ;  and  in  them  these  resulting  traits  reach  their  extreme. 
As  implied  by  its  name  protein,  the  essential  substance  of  which 
organisms  are  built,  is  remarkable  alike  for  the  variety  of  its  meta- 
morphoses and  the  facility  with  which  it  undergoes  them :  it  changes 
from  one  to  another  of  its  thousand  isomeric  forms  on  the  slightest 
change  of  conditions.  Now  there  are  facts  warranting  the  belief 
that  though  these  multitudinous  isomeric  forms  of  protein  will  not 
unite  directly  with  one  another,  yet  they  admit  of  being  linked  to- 
gether by  other  elements  with  which  they  combine.  And  it  is 
very  significant  that  there  are  habitually  present  two  other  elements, 
sulphur  and  phosphorus,  which  have  quite  special  powers  of  holding 
together  many  equivalents — the  one  being  pentatomic  and  the  other 
hexatomic.  So  that  it  is  a  legitimate  supposition  (justified  by  analo- 
gies) that  an  atom  of  sulphur  may  be  a  bond  of  union  among  half- 
a-dozen  different  isomeric  forms  of  protein ;  and  similarly  with 
phosphorus.  A  moment's  thought  will  show  that,  setting  out 
with  the  thousand  isomeric  forms  of  protein,  this  makes  possible 
a  number  of  these  combinations  almost  passing  the  power  of  figures 
to  express.  Molecules  so  produced,  perhaps  exceeding  in  size  and 
complexity  those  of  protein  as  those  of  protein  exceed  those  of  in- 
organic matter,  may,  I  conceive,  be  the  special  units  belonging  to 
special  kinds  of  organisms.  By  their  constitution  they  must  have 
a  plasticity,  or  sensitiveness  to  modifying  forces,, far  beyond  that 
of  protein ;  and  bearing  in  mind  not  only  that  their  varieties  are 
practically  infinite  in  number,  but  that  closely  allied  forms  of 
them,  chemically  indifferent  to  one  another  as  they  must  be,  may 
coexist  in  the  same  aggregate,  we  shall  see  that  they  are  fitted  for 
entering  into  unlimited  varieties  of  organic  structures. 

The  existence  of  such  physiological  units,  peculiar  to  each  spe- 
cies of  organism,  is  not  unaccounted  for.  They  are  evolved  simul- 
taneously with  the  evolution  of  the  organisms  they  compose — they 
differentiate  as  fast  as  these  organisms  differentiate  ;  and  are  made 
multitudinous  in  kind  by  the  same  actions  which  make  the  organism 
they  compose  multitudinous  in  kind.  This  conception  is  clearly 


704  APPENDIX  D. 


representable    in   terms  of   the   mechanical   hypothesis.     Ev 
physicist  will  endorse  the  proposition  that  in  each  aggregate  th 


ery 

ere 

tends  to  establish  itself  an  equilibrium  between  the  forces  exercised 
by  all  the  units  upon  each  and  by  each  upon  all.  Even  in  masses 
of  substance  so  rigid  as  iron  and  glass,  there  goes  on  a  molecular 
re-arrangement,  slow  or  rapid  according  as  circumstances  facilitate, 
which  ends  only  when  there  is  a  complete  balance  between  the  actions 
of  the  parts  on  the  whole  and  the  actions  of  the  whole  on  the  parts  : 
the  implications  being  that  every  change  in  the  form  or  size  of  the 
whole,  necessitates  some  redistribution  of  the  parts.  And  though 
in  cases  like  these,  there  occurs  only  a  polar  re-arrangement  of  the 
molecules,  without  changes  in  the  molecules  themselves  ;  yet  where, 
as  often  happens,  there  is  a  passage  from  the  colloid  to  the  crystal- 
loid state,  a  change  of  constitution  occurs  in  the  molecules  them- 
selves. These  truths  are  not  limited  to  inorganic  matter  :  they 
unquestionably  hold  of  organic  matter.  As  certainly  as  molecules 
of  alum  have  a  form  of  equilibrium,  the  octahedron,  into  which 
they  fall  when  the  temperature  of  their  solvent  allows  them  to  ag- 
gregate, so  certainly  must  organic  molecules  of  each  kind,  no  mat- 
ter how  complex,  have  a  form  of  equilibrium  in  which,  when  they 
aggregate,  their  complex  forces  are  balanced  —  a  form  far  less  rigid 
and  definite,  for  the  reason  that  they  have  far  less  definite  polarities, 
are  far  more  unstable,  and  have  their  tendencies  more  easily  modi- 
fied by  environing  conditions.  Equally  certain  is  it  that  the  special 
molecules  having  a  special  organic  structure  as  their  form  of 
equilibrium,  must  be  reacted  upon  by  the  total  forces  of  this  or- 
ganic structure  ;  and  that,  if  environing  actions  lead  to  any  change 
in  this  organic  structure,  these  special  molecules,  or  physiological 
units,  subject  to  a  changed  distribution  of  the  total  forces  acting 
upon  them  will  undergo  modification  —  modification  which  their 
extreme  plasticity  will  render  easy.  By  this  action  and  reaction 
I  conceive  the  physiological  units  peculiar  to  each  kind  of  organ- 
ism, to  have  been  moulded  along  with  the  organism  itself.  Set- 
ting out  with  the  stage  in  which  protein  in  minute  aggregates, 
took  on  those  simplest  differentiations  which  fitted  it  for  differ- 
ently-conditioned parts  of  its  medium,  there  must  have  unceas- 
ingly gone  on  perpetual  re-adjustments  of  balance  between  aggre- 
gates and  their  units  —  actions  and  reactions  of  the  two,  in  which 
the  units  tended  ever  to  establish  the  typical  form  produced  by 
actions  and  reactions  in  all  antecedent  generations,  while  the 
aggregate,  if  changed  in  form  by  change  of  surrounding  condi- 
tions, tended  ever  to  impress  on  the  units  a  corresponding  change 
of  polarity,  causing  them  in  the  next  generation  to  reproduce  the 
changed  form  —  their  new  form  of  equilibrium. 

This  is  the  conception  which  I  have  sought  to  convey,  though 
it  seems  unsuccessfully,  in  the  Principles  of  Biology  ;  and  which  I 
have  there  used  to  interpret  the  many  involved  and  mysterious 


ALLEGED  SPONTANEOUS  GENERATION,  ETC.   705 

phenomena  of  Genesis,  Heredity,  and  Variation.  In  one  respect 
only  am  I  conscious  of  having  so  inadequately  explained  myself, 
as  to  give  occasion  for  a  misinterpretation — the  one  made  by  the 
Westminster  reviewer  above  referred  to.  By  him,  as  by  your  own 
critic,  it  is  alleged  that  in  the  idea  of  "  inherent  tendencies  "  I  have 
introduced,  under  a  disguise,  the  conception  of  "  the  archaeus,  vital 
principle,  nisus  formativus,  and  so  on."  This  allegation  is  in  part 
answered  by  the  foregoing  explanation.  That  which  I  have  here 
to  add,  and  did  not  adequately  explain  in  the  Principles  of  Biology, 
is  that  the  proclivity  of  units  of  each  order  towards  the  specific 
arrangement  seen  in  the  organism  they  form,  is  not  to  be  under- 
stood as  resulting  from  their  own  structures  and  actions  only ; 
but  as  the  product  of  these  and  the  environing  forces  to  which 
they  are  exposed.  Organic  evolution  takes  place  only  on  condi- 
tion that  the  masses  of  protoplasm  formed  of  the  physiological 
units,  and  of  the  assimilable  materials  out  of  which  others  like 
themselves  are  to  be  multiplied,  are  subject  to  heat  of  a  given 
degree — are  subject,  that  is,  to  the  unceasing  impacts  of  undula- 
tions of  a  certain  strength  and  period ;  and,  within  limits,  the 
rapidity  with  which  the  physiological  units  pass  from  their  indefi- 
nite arrangement  to  the  definite  arrangement  they  presently  assume, 
is  proportionate  to  the  strengths  of  the  ethereal  undulations  fall- 
ing upon  them.  In  its  complete  form,  then,  the  conception  is 
that  these  specific  molecules,  having  the  immense  complexity  above 
described,  and  having  correspondent^  complex  polarities  which 
cannot  be  mutually  balanced  by  any  simple  form  of  aggregation, 
have,  for  the  form  of  aggregation  in  which  all  their  forces  are 
equilibrated,  the  structure  of  the  adult  organism  to  which  they 
belong ;  and  that  they  are  compelled  to  fall  into  this  structure  by 
the  co-operation  of  the  environing  forces  acting  on  them,  and  the 
forces  they  exercise  on  one  another — the  environing  forces  being 
the  source  of  the  power  which  effects  the  re-arrangement,  and 
the  polarities  of  the  molecules  determining  the  direction  in  which 
that  power  is  turned.  Into  this  conception  there  enters  no  trace 
of  the  hypothesis  of  an  "  archaeus  or  vital  principle ; "  and  the 
principles  of  molecular  physics  fully  justify  it. 

It  is,  however,  objected  that  "  the  living  body  in  its  develop- 
ment presents  a  long  succession  of  differing  forms ;  a  continued 
series  of  changes  for  the  whole  length  of  which,  according  to  Mr. 
Spencer's  hypothesis,  the  physiological  units  must  have  an  '  in- 
herent tendency.'  Could  we  more  truly  say  of  anything,  '  it  is 
unrepresentable  in  thought  ? '  "  I  reply  that  if  there  is  taken  into 
account  an  element  here  overlooked,  the  process  will  not  be  found 
"  unrepresentable  in  thought."  This  is  the  element  of  size  or  mass. 
To  satisfy  or  balance  the  polarities  of  each  order  of  physiological 
units,  not  only  a  certain  structure  of  organism,  but  a  certain  size 
of  organism  is  needed;  for  the  complexities  of  that  adult  struc- 


70C  APPENDIX  D. 

ture  in  which  the  physiological  units  are  equilibrated,  cannot  be 
represented  within  the  small  bulk  of  the  embryo.  In  many  minute 
organisms,  where  the  whole  mass  of  physiological  units  required 
for  the  structure  is  present,  the  very  thing  does  take  place  which 
it  is  above  implied  ought  to  take  place.  The  mass  builds  itself 
directly  into  the  complete  form.  This  is  so  with  Acari,  and 
among  the  nematoid  Entozoa.  But  among  higher  animals  such 
direct  transformations  cannot  happen.  The  mass  of  physio- 
logical units  required  to  produce  the  size  as  well  as 'the  structure 
that  approximately  equilibrates  them,  is  not  all  present,  but  has 
to  be  formed  by  successive  additions — additions  which  in  vivipa- 
rous animals  are  made  by  absorbing,  and  transforming  into  these 
special  molecules,  the  organizable  materials  directly  supplied  by 
the  parent,  and  which  in  oviparous  animals  are  made  by  doing 
the  like  with  the  organizable  materials  in  the  "  food-yelk,"  de- 
posited by  the  parent  in  the  same  envelope  with  the  germ.  Hence 
it  results  that,  under  such  conditions,  the  physiological  units  which 
first  aggregate  int2  the  rudiment  of  the  future  organism,  do  not 
form  a  structure  like  that  of  the  adult  organism,  which,  when 
of  such  small  dimensions,  does  not  equilibrate  them.  They  dis- 
tribute themselves  so  as  partly  to  satisfy  the  chief  among  their 
complex  polarities.  The  vaguely -differentiated  mass  thus  pro- 
duced cannot,  however,  be  in  equilibrium.  Each  increment  of 
physiological  units  formed  and  integrated  by  it,  changes  the  dis- 
tribution of  forces :  and  this  has  a  double  effect.  It  tends  to 
modify  the  differentiations  already  made,  bringing  them  a  step 
nearer  to  the  equilibrating  structure  ;  and  the  physiological  units 
next  integrated,  being  brought  under  the  aggregate  of  polar  forces 
exercised  by  the  whole  mass,  which  now  approaches  a  step  nearer 
to  that  ultimate  distribution  of  polar  forces  which  exists  in  the 
adult  organism,  are  coerced  more  directly  into  the  typical  struc 
ture.  Thus  there  is  necessitated  a  series  of  compromises.  Each 
successive  form  assumed  is  unstable  and  transitional :  approach 
to  the  typical  structure  going  on  hand  in  hand  with  approach  to 
the  typical  bulk. 

Possibly  I  have  not  succeeded  by  this  explanation,  any  more 
than  by  the  original  explanation,  in  making  this  process  "  repre- 
sentable  in  thought."  It  is  manifestly  untrue,  however,  that  I 
have,  as  alleged,  re-introduced  under  a  disguise  the  conception  of 
a  "  vital  principle."  That  I  interpret  embryonic  development  in 
terms  of  Matter  and  Motion,  cannot,  I  think,  be  questioned. 
Whether  the  interpretation  is  adequate,  must  be  a  matter  of 
opinion ;  but  it  is  clearly  a  matter  of  fact,  that  I  have  not  fallen 
into  the  inconsistency  asserted  by  your  reviewer.  At  the  same 
time  I  willingly  admit  that,  in  the  absence  of  certain  statements 
which  I  have  now  supplied,  he  was  not  unwarranted  in  represent- 
ing my  conception  in  the  way  that  he  has  done. 

(n 


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